Everyone knows about 24, Family Guy, Seinfeld, and all of the other shows that may float your boat. What the average person does not know about is the fantastic new trend in which studios are releasing single season programs that did not succeed, but have garnered underground attention. Here are a few that I'd like to share:
Judd Apatow's Freaks and Geeks & Undeclared
Let me just start this off with a "holy @$*%"! How did these shows not survive? I mean seriously. They are ridiculously good. Intelligent humor with a good mix of drama. Imagine Apatow's neoclassic 40-Year-Old Virgin produced in a series form for television. I mean it, they are that good.

On the other hand, Undeclared focuses on a group of kids adjusting to college life. From the first episode, when the kids move into their freshman dorms, you will be laughing your ass off. Further humor unfolds when Steven's dad gets a divorce and decides to party it up with his son's friends (on a regular basis). I remember when both of these shows originally aired and it absolutely blows my mind that they were cancelled. As much as I liked Apatow's flick, I wish he could find a platform to develop further TV series.
The Adventures of Brisco County, Jr.
Ok, I admit it. I'm a HUGE Bruce Campbell fan. I'm not alone on this, but it blows my mind that so many people have no idea who this dude is. If you don't, do yourself a favor and rent Army of Darkness. Sure, you may think that I'd recommend anything that Mr. Campbell has appeared in over the years and, to some extent, you'd be right. He's incredible. If you are looking for other good movies, check out Bubba Ho-Tep or one of the other Evil Dead flicks (Army of Darkness is part 3 of the trilogy.) His books are also great, although I prefer "If Chins Could Kill" slightly over "Make Love the Bruce Campbell Way." He's known almost as much for his cameos in films (Spider-man) as he is for his own projects.

Another Bruce Campbell series, Jack of All Trades, was also recently released on DVD. As I missed the show when it originally aired (I had no idea that BC was the star), I can't comment on it yet. Once I finish Brisco, I'll let you know what I think.
Wonderfalls
This is the only series that I don't remember originally airing. I'm extremely glad that I was able to discover this gem. Personally, I feel like summing up any of these series in a simple blurb is an injustice, but here I go again:
This show follows a girl who recently graduated from an excellent undergraduate institution only to end up back home in Niagara Falls, where she sells trinkets at a souvenir shop.

Others that I do not own, but I've heard good things about:
Life as We Know It - Same producers as Freaks and Geeks
American Gothic - Produced by Sam Raimi (director of Spider-Man, Evil Dead, Army of Darkness [see above]). I've heard wonderful things about this one. This one may be my next purchase.
Firefly - Huge cult following. Story continued in the film Serenity.
Greg the Bunny - Hugely popular show that briefly aired on FOX, featuring a cast of puppets and Seth Green. Found another home on IFC.
Profit
Miracles