I am just curious about this subject as well and so I've look around a bit and found this:
The first is from
www.bwgen.com. The software is shareware, so first month is free. And something like $40 to register.
This latter site has freeware to make your own.
http://vhypno.sourceforge.net
I've been trying the first the most mainly for relaxation, sort of works. Not all of the waves work on all of the people. Hopefully the latter is even more effective since it also allows visual cues as well.