If you're looking for chartable COT data that you can run system tests on, and apply indicators, then try http://www.shatterfield.com . You need your own charting software that supports either MetaStock format, or ASCII (text) importing.
You can just pay eSignal for CBOT data. It will still run you about $129/month. We just trade the YM and most of our traders are using enSign, Trade Station or eSignal. I also think Investor/RT has a good CBOT only package. Hit up google.