Here's a few stations Ive been regularly enjoying. They are all very niche, and as so, Im not sure how many here would like them, but, whatever -
For New Orleans music including obscure Zydeco, Mardi Gras Indians/Second Line, and French Cajun:
Mr. Po Boy's Jambalaya Jam
http://www.pocreations.com/indexwo.html
(Then click link that says "New Orleans Radio")
+++++++++++++
Baroque Plus
Yup, nothing but Baroque - glorious if you like it and filled with rare nuggets and composers Id never even heard of before-
http://www.live365.com/stations/arias
+++++++++++++
Swirly Girl -
Darkwave, Girly and Shoegazer (what a great sub-niche)
http://www.live365.com/stations/shoegazergabby
As far as I know these are Internet Only.