Google Hangouts - Web-based - Video conferencing for up to 10 participants. www.google.com/hangouts/
Meetings.io - Web-based - Free persistent video conferencing rooms for up to 5 people - http://meetings.io
Emeet.me - Web-based - Free video conferencing for up to 5 people - http://emeet.me
Teambox - task management, file sharing, discussion and integrated scree-sharing and HD videoconferencing for up to 5 people for free.
Hall.com - Free video conferencing for up to 6 people on Windows, Mac and Linux - http://hall.com
Camdip - free - video group chat - no registration required - for up to 6 users - http://camdip.com
BigMarker offers free unlimited webinars and web conferences with up to 100 attendees - web-based - up to 12-way video conferencing and screen sharing with recording facility - www.BigMarker.com
Ninchat - Video IRC - persistent rooms that can be set to be "public" or "private" - up to 12 people concurrenctly can video chat - http://www.ninchat.com
Pligus - Web-based - Free collaboration and video conferencing for up to 4 people. http://www.pligus.com
Mighty Meeting - Live web presentations with PDF and PowerPoint files across devices and OSes - free - up to 6 video-conferencing participants.