Keep in mind that the PWM signal used by our speed controllers (Victors/Jaguars) is taken from the R/C world for controlling servos. Sounds like what you want is an R/C "Servo Tester".
You can buy them premade reasonably cheap:
http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXVK79 or you can make your own.
Just Google "Servo Tester" and you will find tons of links to circuits, plans, kits, and pre made units.
Another option would be to look somewhere like
www.Parallax.com. They sell various borads and microcontrollers that are designed to drive servos (PWM signals) that you might find useful. A Board of Education and a Basic Stamp might be just what you are looking for or maybe a serial or USB servo controller might could be used to control your motors via a laptop?
Check places like Trossen Robotics and any of the other robotics related suppliers. They all have neat stuff that will generate the PWM signals you require.