There are now two primary governing bodies sanctioning whitewater rescue courses: Rescue 3, and the American Canoe Association (ACA).
The Rescue 3 courses are primarily aimed at rescue professionals such as EMT's, fire fighters and raft guides. As such, these courses are more general in nature and have a heavier emphasis on logistics (ie what the chain of command is when various agencies are invoved in a rescue). They are good, intense rescue courses and after passing the course you receive an official ceritfication from Rescue 3 which will impress your friends and neighbors and might actually mean something in the event you have to deal with local authorities during a rescue. Rather than going into detail on the courses, I will suggest that the Whitewater Rescue Technician course (WRT as opposed to SRT- Swiftwater Rescue Techinchian) is the most applicable for recreational boaters. If you need the cert for guiding rafts, then go for SRT.
The ACA courses do not result in a certification which would be recognized by authorities, but they are much more tailored to recreational boaters, and deal with situations which are more realistic for kayakers- like suppose for instance that you don't happen to be carrying 200 feet of static 11mm rope in your kayak!

The ACA basic course is one day and is a good intro to rescue, and the advanced course is two days and covers most scenarios that you will encounter as a recreational boater (including various pin situations).
Good summary descriptions of all of the courses that I mentioned can be found at:
http://www.wavetrek.com/washington_rescue_training.htm
If you are interested in taking the ACA rescue courses locally, the Colorado White Water Association offers both beginning and advanced ACA courses to members, and the course fees will go to support river access and conservation in Colorado. Contact Phillip Bowman at (970) 328-2037.
If you are interested in taking Rescue 3 courses, Brandon Holms of Adventure Medicine International is offering several WRT courses in May- his contact info is:
Brandon Holmes
info@rivermedic.com
970.389.7441
Cheers!
Marco