US-centric: Find potential roommates with Google maps mashup webapp Roomapes. To list your residence, enter a profile complete with rent amount, housing situation, listing description, and a picture. Search for available shares by geographic region or by zip code. Text listings (without the Google Maps) are also available. Roomapes is free and requires an email address to post yourself as an roommate who is seeking a new dig or to manage your listing. If you're looking for a new apartment, also consider previously mentioned Google Maps/Craigslist Mashup MapsKreig.