Wine (OSS): http://www.winehq.com/

Wine Doors (OSS): http://www.wine-doors.org/trac

WineTools (OSS): http://www.von-thadden.de/Joachim/WineTools/

CrossOver Office: http://www.codeweavers.com

Cedega (for games): http://www.transgaming.com/

Wine How To: http://www.frankscorner.org