What is a good, upbeat, summer song to use in a video I am making?

Temper Trap are alright, but have you heard of Passion Pit's "Little Secrets"? You'll either love it or hate it. Sounds like you are searching for something fairly modern but also not mainstream (eg hasn't been played on radio 400,000 times). Passion Pit are fairly well-known, so sorry if my suggestion isn't what you are looking for :)