Hey @Alvin Grier vacant properties are a great way to find deals. You can use bird dogs to find vacant properties for you. Just post ads on Craigslist, Ebay Classifieds, Oodle, and Backpage that you're looking for bird dogs. You might even be able to find some in the "Real Estate Services Offered section". That being said, I really like @Todd Plambeck's idea as that is a one shot stop to get loads of leads quickly.
@Avery Gilmer is definitely right that driving for dollars works but I still prefer to use bird dogs who you can either pay per lead, based on the information they submit and/or upon closing a deal. There are a lot of people interested in real estate investing and this is a way for them to get their feet on the ground.
There is also software out there that can find these vacant houses as well. It's not 100% perfect but works pretty well. Depending on your state, mailing list companies have lists of vacant houses too in some cases.