Here are a couple useful lists of German verbs and their principal parts (except for list 5 which is just a simple list of infinitives). I found these lists searching the Internet, so I can't vouch for their accuracy until I've had a chance to look closely at each of the entries. My goal is to somehow programmatically combine these lists into one master list with a unified format. And while doing that, I hope to check each and every word for accuracy. In the meantime, I hope someone other than me finds this information useful.