Hudhomestore.com â€“ Official website for searching for Government owned homes
Bidselect.com â€“ Another site that has REOs
Homepath.com - Fannie Mae owned homes
Homesteps.com â€“ Freddie Mac owned homes
Gohoming.com - Another site that has REOs
reo.wellsfargo.com/WBREOHome.aspx - Wells Fargo REOs
These are just a few, but Fannie and Freddie are the biggest. You will be able to search plenty with these sites.
Hope that helps.