Weekend Treasure - Online postings of North American garage sales and estate sales, associated with online maps. - http://www.weekendtreasure.com/
Yard Hopper - Database for sales in major U.S. cities. - http://www.yardhopper.com/
Yard Sale Canada - Database for sales, with advice on conducting and visiting garage sales. - http://www.yardsalecanada.com/
Garage Sale Nation - Listings for sales in the United States. - http://www.garagesalenation.com/
Garage Sales Australia - Database of user-posted listings for upcoming sales, with advice and blogs about the experience. - http://www.egaragesales.com.au/
Garage Sale Hunter - Offering a list of sales throughout the United States. - http://www.garagesalehunter.com/
Garage Sales Source - Local sale listings in North America, plus articles about running sales and finding bargains. - http://www.garagesalesource.com/
QuickGarageSale.com - Find and post free garage sale advertisements (North American locations). - http://www.quickgaragesale.com/
Wikipedia: Garage sale - Online encyclopedia article about informal, irregularly scheduled events for the sale of used goods by private individuals. - http://en.wikipedia.org/w/index.php?title=Garage_sale
Garage Sale Network - Shares data between garage sale websites. Submit information about planned sales, create maps before a day of shopping, or download GPS data. Registration required. - http://wiki.carterfamily.ca/tiki-index.php?page=Garage+Sale+Network