Free Mac program: http://www.google.com/tools/dlpage/res/talkvideo/hangouts/
Free Windows program: http://www.google.com/tools/dlpage/res/talkvideo/hangouts/
Website: http://www.google.com/tools/dlpage/res/talkvideo/hangouts/
Google Chrome app: https://chrome.google.com/webstore/detail/google%2B-hangouts/kbpgddbgniojgndnhlkjbkpknjhppkbk