I use human heat pads from Wal-Mart... they're about 10 bucks, and come with a temp control. I couldn't tell you specific temperatures, but I can make the heat subtle, or very, very warm.
What kind of animals will you be using the heat pad for? I know some UTH's have rheostats but are expensive... I'll try and find out who makes them for you...
Hope this helped a little...