newby at BCI ??
read this very good survey by the (muy sympathico and very competent) Christophe Guger from (the beautifull city of) Graz. Or better yet pay him a visit in bejing (at HCII 2007 in Beijing from July 25 to 27, 2007). And don't forget to pay him my regards and say hello from georges.
Visit his website for nice tutorials and video's as a general but very good introduction to this (fascinating) subject.