I second (or 3rd, 4th, whatever):
The Philadelphia Story
It Happened One Night
Love, Actually (this is such a wonderful movie on so many levels)
and add my own selection:
My love for John Hannah after seeing this movie knows no limits.
Thanks for all the great ideas so far!
Actually I have seen a few of them already (Wimbledon - which I really liked, but I’m not sure if it’s on DVD yet), and Keeping The Faith (it was a while ago, but I remember it being really funny). From what I’ve heard about the plot, it would be easy to split the viewing Love Actually over two days.
And I’ll be sure to mention a bunch of the more classic films. (Out of 60 or so employees at my company, about 55 are women aged 30 to 50, so they’ll get some nostalgia out of the older films).
Love Actually
Fever Pitch
My Name Is Joe
Garden State is a romantic comedy? I mean, I know it has romance and it has comedy but I wouldn’t call it a romantic comedy.
It is. I work at Blockbuster and we have it on our shelves for rental and for sale.
I can’t believe I forgot The Philadelphia Story - the dialogue just hooks me every time, which is the same quality I like so much in When Harry Met Sally.
When Harry Met Sally… was the first one I thought of. And everyone else, too, apparently.
So in search of some novel suggestions, let’s drop by Lubitsch Alley:
*The Shop Around the Corner
Ninotchka
Trouble in Paradise
To Be or Not To Be *(not exactly a romantic comedy, but great)
and Austen Lane:
Emma
Sense and Sensibility
Mansfield Park (I haven’t seen it all the way through, but it looks pretty good)
Twentieth Century is Carole Lombard at her best.
Truly Madly Deeply (a little dark and offbeat, but good)
Choose Me (a little-known favorite of mine by Alan Rudolph)
and we can end up in heaven:
Made in Heaven (Rudolph again)
Defending Your Life
OK, maybe it’s a little short on romance. And on comedy. But it’s a damn fine flick, and not just on Valentine’s day.
I have to second Sliding Doors.
My cousin and his wife watched it and hated it vemonously. Turned it off shortly into it.
We rented it and really liked it.
So now, whatever they hate, we know we will like. And vicey-versy.
And I am with you on the John Hannah Adoration thingie.
Another good one: Next Stop Wonderland.
Clueless
My favorite in the genre is The American President
(Run time, 114 min)
The IMDB sums up the plot well, and I think that the casting is very well done (especially with Richard Dreyfuss and Michael J. Fox in support). It’s romantic without being gushy, and funny without being stupid (not to say that that’s a bad thing all of the time 
)
::Windwalker shakes his head::
Breakfast at Tiffany’s.
::Windwalker exits stage left::
Gregory’s Girl and Local Hero, both directed by Bill Forsyth. The former emphasizes romance more than the latter but they’re both very good and very sweet without being saccharine.
Prizzi’s Honor
Bride of Chucky
Scream Blacula Scream
I’m really not in the spirit of this, am I?
Although not a big fan of Diane Keaton, I liked Something’s Gotta Give.
A classic would be 7 Year Itch.
Also Something About Mary and Tin Cup.
Hey, at least you didn’t recommend House of Sand and Fog.
I second (or octuple) the following:
Love, Actually
Roxanne
Sliding Doors (Possibly your best bet, since not many will have seen it, and it’s very good.)
I wouldn’t go with When Harry Met Sally only because I saw it way too many times already. Strangely, I would still recommend Overboard, which I have seen even more times. But if you have some Meg Ryan fans to please, I’d go with Kate & Leopold.
If they could handle a more dramatic movie with romance in the mix, I’d also toss in Beautiful Girls and Laurel Canyon.
My favorite romantic comedy of all is probably The Wedding Singer. It helps that it squarely targets the 30-somethings who came of age in the 80s.
It’s not a great movie, but it’s cute and funny, at least in parts, and it has James Garner. That right there is worth a bunch of points. I’ll watch James Garner any day.
Murphy’s Romance
Not sure about the spelling there, actually.
And it probably has the advantage of not being something everybody has seen a dozen times. Other than that I’d put in a good word for It Happened One Night and Philadelphia Story.
Gotta second this one.
Actually, 10 Things I Hate About You is a well-done and fun adaptation of The Taming of the Shrew. Good romantic comedy and, unlike Romeo and Juliet…
… no one dies. Well, no one stabs themselves. Or poisons themselves. Or, hell, hires Leonardo Di-what’s-his-name to play a part.
I’d like to second a number of movies mentioned already:
While You Were Sleeping
The Princess Bride
I’m also a bit of a Cary Grant fan, and love some of his less well known films:
I Was a Male War Bride - for a period farce it stands up very well to modern sensibilities
People Will Talk - another period piece, though not a farce, and again, it stands up very well in spite of the 50 years since it was filmed.
Father Goose
Actually that’s exactly what I thought but I threw it in there anyhow because it did, in fact, have both romance and comedy.