David Attenborough would be my choice.
I have serious doubts that Gould should properly be included in any list of real contenders. I would argue that any genuine candidate must be someone who was widely respected both by those in the candidate’s own scientific specialties as well as the mainstream scientific community, and that, I contend, should end up excluding Gould. He was famously (or perhaps infamously, depending on one’s own opinion) insulted in print by John Maynard Smith, easily one of the world’s most predominant and respected evolutionary biologists, when he wrote:
(As a personal aside, I find that statement to be rather self-contradictory, for there Smith was, publicly criticizing Gould!)
I share the view of many leading scientific lights who thought that Gould’s politics (he was an avowed Marxist) seriously impaired his scientific objectivity and thus his credibility, particularly in his feuds with E. O. Wilson and other cautious sociobiologists and evolutionary psychologists, who rejected Gould’s Marxist, pseudo-religious ideological belief in the inevitable historical perfection of humankind. There was an undue amount of political bias in Gould’s widely acclaimed book The Mismeasure of Man, for example. And he stirred up extensive and, I think, well-justified criticism for propounding his notion of “Non-Overlapping Magisteria”, which is widely seen by skeptical scientists as a bogus concept apparently designed to immunize religious beliefs from scientific scrutiny and analysis.
To be fair, however, I must note that some mainstream scientists saw Carl Sagan as a bit of a pretender to the throne, too, in the sense that a few remarked that he was considerably behind the times in the domain of planetary science. My own view is that even if that were true, it’s a trite criticism, as Sagan was very highly respected and admired by the larger scientific community and by the public. And he was so to a degree far greater than Gould could have ever even approached.
Finally, my own list of the most influential promoters of science and the philosophical outlook it embodies would include Martin Gardner, Carl Sagan, Isaac Asimov (“s”, not “z”, Yllaria), Bill Nye, E.O. Wilson, Ray Hyman, and Paul Kurtz.
I’m tempted to add James Randi as well as to second Typo Knig’s nomination of Johnny Carson, who took significant risks by putting alleged “psychics” like the vile Uri Geller to valid, on-air tests (typically guided behind the scenes by Randi). These tests were risky for Carson because the studio audience, as well as those watching on TV, often became very quiet and uncomfortable for the sometimes-considerable duration of the excruciating failure. You can bet your ass the Network people were not at all fond of Johnny’s ventures into these still, quiet moments, so the fact that he insisted on continuing such tests involved power contests with NBC executives – contests Carson obviously won. Hooray for Johnny Carson!
But neither Randi nor Carson were scientists themselves, so they wouldn’t make my own personal list.
I can’t believe there’s no love for Gene Ray. You are all educated stupid!
I suspect most of the people here aren’t old enough to remember a time when Magnus Pike was the archetypal face of science. I know I eagerly awaited each episode of “Don’t Ask Me” so that I could enjoy the mad scientist spectacle of Magnus Pike explaining how the Universe worked while simultaneously swatting hundreds of invisible flies.
Patrick Moore has brought an incredible number of people to astronomy,not just from the sky at night but from his personal actions in normal life.
Steven Hawkings for obvious reasons.
David Attenborough for his totally incredible documentaries.
Been said up thread but heres another endorsement ,Carl Sagan.
Also Science fiction authors,Robert Heinlein,Issac Asimov and Arthur C.Clarke.
A shout out for CSI.
YES! I absolutely adore this man, perhaps unhealthily so. I have always been fascinated with science in general, physics in particular, but had tons of trouble getting my head around the concepts. I first heard Tyson on Science Friday on NPR (this is his most recent appearance:linkity link) and was shocked that I actually followed what he said. I understood someone talking about Astrophysics … that is fairly amazing. I immediately went out and bought his book, which he talks about here (it’s almost two hours, but if you have time you really oughta watch it … he is extremely entertaining).
And, wouldya look at that … he will apparently be on Colbert Monday.
Dr. Tyson has an thread of his own [thread=504458]from January[/thread]. Some wag 
killed the thread with a link to Tyson’s first appearance on The Colbert Report, just a few days after The Report started. The video is made of genius.
Thomas Dolby
She blinded me with science 
Declan
Despite the often poor representations of the reality of science, I think they do a decent job of bringing the idea of critcal thinking to the masses more than many give it credit for. What it looks like at first glance vs. what it really is a recurring concept.
I totally agree with the likes of Sagan, and Hawking, but I wouldn’t call them the most recent. The most popular and successful, sure.
I’m down with Adam and Jamie from MythBusters, Bill Nye, and even the more niche Brian Greene on theoretical physics.
But I think Michio Kaku definitely deserves a mention here. This guy is everywhere now, and I believe he wants to fill Sagan’s shoes (some big shoes, IMHO). He’s even got his own chunk of programming, with ScIQ Sundays on The Science Channel.
The OP said ‘recent memory’, so I’d put that down to anyone in the past 40 or 50 years.
I did. 
Gah! Sorry, Johnny, missed that!
No worries. And I agree. Michio Kaku is one of my current faves.
No love for Don Herbert (Mr. Wizard)? Bill Nye probably watched Mr. Wizard. It’s likely a lot of other scientists in their 30s through 60s probably did too- he was on the air from 1951-1972 and from 1983-1990.
The original run was before my time. I did catch a couple of episodes a few years ago though. He seemed a bit of a Grumpy Old Man, and the kids seemed entirely too wholesome.
Loved Mr. Wizard. Watched him when he was on the air in the 80s. He’s responsible for me having set my eyebrows (and almost my parents house) on fire when I was a kid.
You may well be right, but the negative impact of C.S.I. must be considered as well. Many prosecutors in the U.S. complain that a rapidly increasing number of juries in high-stakes criminal cases are demanding they provide roughly the same quality and extent of high-tech evidence that they see on C.S.I., much (perhaps most) of what they see existing only in the realm of science fiction. As a result, a number of prosecutors claim that juries are acquitting defendants that would previously have been convicted.
My hunch is that in at least some cases, this is probably a good thing. But I also think there are cases where it’s not a good thing at all.
Disagree. First how widely and forcefully he is disparaged is arguable. While he had many detractors, critics and enemies in his field, he also had supporters, admirers and allies. Even his fiercest critics generally acknowledged his knowledge and ability as a science historian and essayist, if not as an actual scientist.
And while one can disagree with his scientific ideas ( I found his views on systematics pretty dated even in the late 1980’s when I actually paid attention to such things ), there is no doubt that he actually stimulated debate and enquiry within his field, whether his ideas held up or not. He was not a crap scientist, by any means. Though I’ve never read his snail work, so I have no idea how any of that holds up ;).
But I think all of the above is beside the point. As a popularizer of science, he was aces and I think his ability as a scientist and standing in the scientific community is almost irrelevant to that. I think he loses out to Sagan and a few others ( I think your choices are all solid ), but he is easily on the the level of a Stephen Hawking.
“Stephen Gould is the best writer of popular science now active. . . . Often he infuriates me, but I hope he will go right on writing essays like these.”
- John Maynard Smith
CSI deserves credit for presenting science in a very popular format. Shows like Mythbusters or Bill Nye may be more science-oriented but anybody watching those shows is likely to already be sold on science. CSI reaches out to people who might otherwise never see science in entertainment.
And CSI shows people using science in the real world (or at least the TV version of the real world). The scientists on CSI are working cops solving crimes; they’re putting science to work. They’re not the stereotypical scientists off in some ivory tower.