Scott,
I'm no expert, but I ran a "dethatcher" over my yard last fall before overseeding. There wasn't much in the way of thatch, but it was late enough in the year that most of the annual garbage grass/weeds had died off, and the spring tines pulled a lot of the junk up. They also scratched the surface up pretty well, so there was good ground contact for the seed. I'm quite pleased with the results.
I had one of those $99 special GT dethatchers from Home Depot. I ended up bolting it on to a sleeve hitch to cat0 three point hitch adapter I have and used it that way. It's only cat 0, but the adapter comes in handy for ad-hoc contraptions such as this, at least until I learn to weld.
Kevin