iSay

The Ipsos iSay survey panel is a gift certificate / prize panel.

Panelists who complete surveys are awarded points that can be redemed for gift certificates to a long list of  merchants (they have a LOT of choices here, more so than other gift certificate panels) as well as for various prizes including electronics like iPods (although you need quite a few points for that).  They also run contests for panel members and award prizes to active panelists.