Both X files and Milleneum have great intro music, as does ER.
I second the call about the excellent use of music within the wonder years.
Theme music for a currently running show: NYPD Blues
Memerable music from older shows:
Twin Peaks, very moody.
And Northern Exposure a real blend of esoteric and often obscure stuff. The only show where we would watch the credits closely to see if they would relent and name the artists. They never did, the bastids!
My own personal favorites from long ago: the Peter Gun theme, and the theme from MASH***.
Twin Peaks had some of the most brilliant made-for-T.V. music I’ve ever heard, but, for brilliant use of existing music, especially existing pop music, my vote has to go to Buffy the Vampire Slayer. The theme leaves something to be desired, but I still remember a sequence set to The Cure’s “Watching me Fall.” Oh, but I suppose I should give honorable mention to The West Wing for the montage set to Jeff Buckley’s cover of “Hallelujah” in last season’s finale.
Girls were girls and men were men
Mister we could use a man like Herbert Hoover again (why?)
Didn’t need no welfare state (well, I do, since I’ve been laid off)
Every body pulled his weight,
Gee, our old LaSalle ran great (took me twenty years to figure that one out)
Those were the days (until that annoying dark-haired girl came on the show)!
The Equaliser. Can’t beat it.
Ooh, the Equaliser, good call.
On British TV (probably on Masterpiece Theatre in the US), the theme tune to Inspector Morse is perfect for that series.
What about Barney Miller?
That was just on TV here tonight (we are so far behind it’s not funny), and I thought that sequence was brilliant.
Theme song; Six Feet Under, by Thomas Newman.
Doctor Who, especially the main theme and the music from the Pertwee era (I’m thinking Sea Devils here).
yosemitebabe already mentioned Cosmos.
And of course, <singing>Kyuun kyuun, kyuun kyuun, watashi no kare wa pilot</singing>. Bubblegum pop: humanity’s last hope 
Come ‘n’ listen to my story
‘Bout a man named Jed,
A poor mountaineer
Who barely kept his fam’ly fed
An’ then one day
He was shootin’ at some food
An’ up from the ground
Come a’ bubblin’ crude
Oil, that is… black gold… Texas tea…
You know the rest.
I’m surprised that I am the first to mention The Addams Family.
As for instrumentals, I’d mention Quantum Leap, Batman, the Animated Series and Airwolf.
The Jeffersons, LA Law, and Boston Public are all good choices. And Mystery! too- very creative one there.
I also like the theme to “Frasier”- the opening one is cool. Brief, but nice, and I like the closing theme, as performend by Kelsey Grammer.
Oh, and one other one…huge guilty pleasure, but “Sailor Moon.” The theme song is good. (What? It’s catchy!!) And the music they play when they show the title of the episode. Also the background music for whenever they’re with the Negaverse. The high pitched sort of droning one.
Just remembered another one myself - the theme for Hitchhiker’s Guide to the Galaxy. I know it was an Eagles song, for all it didn’t sound like it; think it was called Journey of the Sorceror.
When I saw the title of the thread, I first thought of Cowboy Bebop. I can’t believe that all that music was written by one person – Yoko Kanno is my hero.
Other great themes are Space: 1999 and Lost in Space (both versions).
Angelo Badalamenti’s work for Twin Peaks (and Wild at Heart and Blue Velvet as well) was magical.
I’m the only one impressed with what Christopher Franke did on Babylon 5? The third and fifth season themes alone held more emotion than entire seasons of various Star Trek series.
In particular, the episode from last season with Burt Reynolds and the Spanish/French/Italian music.
The Star Trek: Voyager theme was my favorite of all the ST series theme music. For currently running series, I like the West Wing theme and CSI’s use of The Who’s “Who Are You?”.
for theme/opening music, Hill Street Blues , hands down.
My wife would say Party of Five , as that was her favorite show. Every time that BoDeans song comes on the radio, she starts dancing around.
The Streets of San Francisco
Man, I love that tune.
Ladies and gentlemen, Cop Rock.
Seriously, most people who claim it was a bad show never saw it. I wouldn’t say it was good, but it was unique and interesting and the music was good.
No, I believe Williams was ripping off a classical composer in this case, but I can’t remember which one. However, I’ve heard an almost identical theme in a 19th century piece. Williams has good taste; ripped of Tchaikovsky and Holdst for Star Wars, Copland for The Cowboys and again for the crappy fanfare they’ve been playing the last couple of Olympics, etc., etc.
Anyway, I don’t think anybody has mentioned The Rockford Files. Unforgettable instrumental theme.
I loved a short-lived show called EZ Streets. It featured a lot of sad, Celtic-sounding music. If any of you saw the scene the cuts between Jamaicans trying to assassinate Jimmy Murtha and the cop having sex with Murtha’s half-crazy lawyer/girlfriend on a cot in the basement of an abandoned tenement, you might remember the song they used. (This one scene establishes a) that the cop and the lawyer have a sad old history together; b) that the young man who had taken a prison sentence in Murtha’s place is bound to Murtha for life; c) that you don’t get happy endings in this show; the best you can hope for is survival. The haunting ballad they use nails the tone down.)
[hijack]Actually I never really figured this show out, because I missed the pilot. I never knew who the hell “Frency” was, or why the police department seems to be a big empty building, or who was really corrupt and working for the bad guys, and who wasn’t. But during its short run that show had some of the most extraordinary scenes I’ve ever seen on tv. (Like the Mayor, in thrall to organized crime, blasted on coke, standing in an abandoned, shut-down factory, reliving his stirring speech from when he was running for city council and promised the factory workers he’d “draw a line in the sand” and save their jobs – trying to recapture a time when he wasn’t corrupted.)[/hijack]
Oh and “The Fishing Hole” from The Andy Griffith Show.