Proofy - Quickly validate and verify your email lists.
KingSumo - Grow your audience with viral giveaways that cut marketing costs
Trumail - Free email verification API
ViralSweep - Grow your fans and increase sales with sweepstakes and giveaways.
Email List Verify - The Fastest Way to Improve Email List Deliverability and ROI
Retweet Picker - Retweet Picker is an online tool that is helping you to select the random winner from Twitter for the giveaways.