Rafflecopter recently announced that they have official compliance from Facebook for their contests, though they had to remove the entry option "like this post" for all contests going forward after July 20th 2012.
This means you don’t have to worry about being non-Facebook compliant if you run a Rafflecopter contest and campaign from your blog post or your fanpage itself since you can embed the Rafflecopter contest into an iFrame tab on your Facebook fanpage if you want.
I tend to run all of my contest on Rafflecopter as it does an excellent job of tracking all of the entries (even with some ability to cheat the custom entries) it makes running contests so much easier. It does only support random winners at the moment, so if you want to run a contest that focuses on building your mailing list and one where the winner is the one who collects the most entries then something like Contest Domination for WordPress is an ideal contest plugin that can really help grow your mailing list quickly and doesn’t use Facebook as entry methods, only subscribing to your mailing list and promoting your contest across social media to get more users to subscribe and enter the contest.
Read more about Rafflecopter and how they are compliant with the Facebook Giveaway Rules and Regulations here: