The best single location for all the free resources is found at Women Learn Thai. Catherine Wentworth has things for all levels. While you are there you can check out interviews of successful language learners to help motivate yourself, especially of yours truly. There is also so much Thai language learning posts there. I was given an opportunity to guest post an article about the Speak Your Language method, which is the basis for my pod casts that I am creating to help teach Thai. It is truly a fantastic site for Thai language learners.
Another good site is found at Tower of Babelfish
A fantastic list of classifiers
Josh Sagers blog is also a good source of language learning materials.