Stephen Colbert and Jon Stewart

Stephen Colbert and Jon Stewart have their own shows, the Colbert Report and the Daily Show, respectively. I'm a fan of both, because it's natural to be a fan of satire when interested in politics, and these two perform satire really well.
Now this might just be me, but when I watch the Colbert Report, its noticeably more intense in the Daily Show, maybe because Colbert or his writers operate best at that degree. When I say intense, I mean more in character and more outspoken against or for certain things.
So with an intense performance every night, Colbert's fan base is quite large, and pretty hardcore (including me). Fans of Colbert gather to make a organization named the Colbert Nation, which make cool things like the Colbert Super Pac possible.
I'd say I'm a member of the Colbert Nation, I've always liked his jokes more than those on the Daily Show, and I go out of my way to express that enthusiasm.
It's also worth noting that Colbert's particularly popular on the internet for his extremely popular parody of what a Republican might be like. Message boards light up with his quotes and image macros, because he and his show are just abundant sources for humor. So it's not hard to see why internet groups have had a history of being great fans for him.
The Word, Tip of the Hat/Wag of the Finger, The Threat-Down, and so many more bits that are always funny, I'm proud to be a fan of the Colbert Report.
I also own Stephen Colbert's book, I Am America And So Can You, which was just fantastic. I actually reread it a couple times since I've first bought it, it was definitely worth getting if you like his brand of humor.

Now Jon Stewart's show is older, and thus gains a bit more authority than the Colbert Report.
There's also the fact that Colbert himself came from the Daily Show and used to work under Jon Stewart that lends more clout to the Daily Show, being the original one and the source for a guy like Stephen Colbert.
Jon Stewart also has a group of younger 'reporters' that parody news teams throughout all the news channels, finding stories in America and abroad that highlight some pretty funny things.
I feel like I can watch the Daily Show with my parents better than I could the Colbert Report, because it's more mellow. It's really informative and it has a brilliant brand of satire all its own, because it was the first show I've ever seen like it.
They are both great shows, if you haven't seen them, you should try them. And if you've been a fan but fell off the routine of watching them, try them again and see if they are worth your time.
I also have two of the Daily Show books, which I can't recommend as highly as I Am America, but that's just a reflection of my taste. There's also the fact that I've only started reading America (the Book): Teacher's Addition, and not his other book Earth (the Book).
I'm excited to read it though, so try it if you've got the time and appetite for this type of satirical humor.