Think Pascal is available for free on http://www.pascal-central.com/ or http://www.lysator.liu.se/~ingemar/tp45d4/think.html . Or do a Google search for "ingemar think pascal".

I'm using ThP for a personal project. Documentation isn't generally available, but I was able to buy a set on Amazon. It's mostly a standard Pascal, so the FreePascal documentation may help.