Ceolas. A veritable treasure trove of information about traditional Irish music.
Slowplayers.org. Lots of traditional Irish music notation in pdf format.
Irish Traditional Music Tune Index..
The ecellent Digital Library of Applachia. Hundreds of free mp3s of Applachian music and much more.
The Canonical List of Banjo Jokes. How many banjo players does it take to change a light bulb? Find out at this site!
EzFolk.com. More clawhammer banjo tablature, tutorials and lots more besides.
The Banjo Hangout
The Fiddle Hangout