Webra 1.45 (head they are coming out with a bigger one, too)
http://www.adis.at/webra/1057/e1057p.htm
Mintor 1.40 and 1.70
http://www.shivlal.com.sg/mintor.html (I don't think this is the official manufacturers page)
YS 140 (FZ, DZ, etc)
http://www.yspower.co.jp/
OS 1.60 (on more sport pattern planes)
ST2300 has also been used, somewhat
Those are the big players. Some people are experimenting with gas, too.
Ed Hartley has a good page with 2 cycle pattern info:
http://www.rcpattern.com/2cycle.htm