I've been seeing lately a lot of giveaways using the Rafflecopter. I think using this service helps the contest host list the requirements to join the contest or giveaway clearer and neater. Also, it is easier to understand also for those who are joining the contest. Maybe if I host a contest someday, I might use this service also, if I get an invite to use them. Rafflecopter is right now an invite-only service.
Anyway, aside from TechieShe's weekly meme giveaway which I try to join weekly, some of the giveaways using Rafflecopter right now are