Try infospace.com for a reverse directory. Sometimes the entries are a bit out-of-date, but overall a good source (considering that it’s free).
If you need a more exact source, you can purchase reverse durectories from the phone company (but they’ll cost you a pretty penny)
You’ll need to talk to a local source about the expired listings. Call several area Realtors, tell them your investing plans, and see who seems interested in your business. Offer a few hundred dollars referal for every one you buy, and you should have takers.
If you’re not a realtor — going into the reverse directories is only going to give you names of the people living there—not expiries. If you’re interested in a particular area of town, you might cruise around and see how long the realtor signs have been up—most listings are approx 90 days. You may decide to approach a For Sale by Owner Vendor face-to-face. Another way would be to go scrounging around the real estate offices for their recycling bins to get a hold of some old MLS catalogues and if you know how to read the listing information you probably can determine when the property expires. Not all realtors put that information down but again you can guess (90 days hence). If you’re going after a property and not sure whether it is listed–go check if the sign is still up. Good luck.