On a number of traffic exchanges they have a feature called Team Surfing, if you join a team and surf at the end of the week you win extra credits, banner and text impressions depending on how well you and your team surf.
I’ve made a number of Team Surfing teams on traffic exchanges. The team is called TE-Tips so just look on the team listing page and feel free to join!
TE-Tips is on the following traffic exchanges and co-ops:
Without teamsurfing you’re missing out on free credits so it’s a great idea to join one and benefit on the whole teams surfing.