Filk, or Fan Music has become almost viable as the internet has allowed groups to unite around smaller and smaller things. Perhaps I a few years there will be people who make their livings writing songs about Knight Rider and Mortal Kombat. A few places where you can find interesting filk songs

The Brobdingnagian Bards - In addition to having cool Filk they are also quite good and have Celtic songs, and have a podcast. If you don't know about Marc and Andrew check out their stuff. Sadly they are currently not active but their stuff is still available.

Filk Archive - An Archive with a wide variety of Filk in both theme and quality. This is a fun place to explore. This site does require you to sign up but it is free and not difficult.

The Geekspin - A Farpoint Media Podcast this show has a theme each episode and plays songs that fit that theme. From Lord of The Rings to Lost there are great and often funny songs. This was my introduction to filk and I still listen to it whenever it comes out.

Jonathon Coulton - I'm not certain if this is technically filk, but its fun music and is certainly aimed towards the same audience as filk. I believe his most popular song is "Re: Your Brains" but he has a lot of other great stuff too.

Eben Brooks - Quite a bit of interesting stuff. His site tends to focus on their, marginally, more mainstream songs while the things they have on youtube tends to be more filk.

A couple songs from youtube








(In an attempt to stir up some controversy I would like to add that written works isn't filk, it's not music until you sing it until then it's just poetry)