What is this thing called "filk music"? Is it a typo? Historically, yes, but it's become a term in its own right. It's not so much a genre as a culture. The most widely accepted concise definition is "the folk music of science fiction and fantasy fandom."
It began with people singing late at night at science fiction conventions, after the scheduled programming was over. Today there are filk clubs and conventions in the United States, Canada, Great Britain, and Germany, and some filk activity in many other countries.
A lot of people think of filk as parody. To "filk" a song means to write new lyrics to an existing tune. But filk has become much more than that. It includes original songs with striking tunes and lyrics.
Some people associate filk with bad singing. The grain of truth in that idea is that we welcome people of all levels of ability and encourage them to sing. Part of the filk culture is the idea that music is ours to make, not just to listen to. In the words of Sally Childs-Helton, "we are taking back our right as human beings to make art."
Everyone is welcome, but some filk performers are highly skilled singers and instrumentalists. They'll sweep you off your feet with performances of their own songs or ones by other people. Some noteworthy filkers started off with minimal skills and then improved tremendously.
You'll find filk in songbooks, in Internet videos, in posted lyrics. But the way to really experience filk is at a filksing. Whether you're new or you're a long-time fan, whether you've got a professional voice or need both hands to hold a tune, you're welcome to join us.
You don't even have to sing unless you choose. You can request songs, ask if people have songs on a given topic (we almost always do), or just enjoy the music and the company.
Here is a partial list of other filk sites on the Web.