I, personally, love yahoorealestate.com It's easy to see whatever is foreclosed upon. It would also be wise to check out the other super good deals, as people might be working to avoid foreclosure by listing cheaply. Put a low-ball figure on list from cheapest to highest price, or oldest listing first. Have a realtor find out the real listing date, as the dates shown are probably just when it was updated. For example, one place I bought showed that it had only been listed for 16 days, but really it had been "on the market" for nearly a year. My realtor straightened that out for me.
Also, look for auctions (Google it), and sign up to receive updates/newsletters for any real estate auction companies in your area. There are several online real estate auctions, but I've never been impressed with them. Maybe you'd have better luck.
And, in an area you might be interested in purchasing within? Drive around and look for signs and/or notices simply pasted on the door and windows of properties. Sometimes there won't be a sign in the yard, but there will definitely be something on the door to alert those people interested and/or for any questions on the property.
Finally, go to your local banks and ask for the person who deals with disposing of foreclosures. Local banks are great for this, and usually can't afford to play hard-ball with you if you make a viable offer.