Banks, FannieMae, FreddieMac, HUD and others all have REOs listed on their sites plus, as mentioned, brokers can help find them for you. I would strongly recommend that you engage an attorney familiar with REO sales as they can be tricky. Your lender may be able to recommend someone who can also close your loan, thus saving on their fee for acting on your behalf as well.
You may find that REOs may need work or are at market price. In such cases they may not be a bargain.