PointsHound is offering an additional 500 bonus miles in any of their associated frequent flier programs (United, Delta, Hawaiian, Aeromexico, airBaltic) with any hotel booking made through the end of March. PointsHound provides a unique double dip service whereby they allow users to earn miles with select airline partners in addition to hotel points (and sometimes elite benefits/stay credits) that would normally only be earned by booking directly with the hotel. Scott over at Hack My Trip provides a full review of the different PointsHound service offerings here as well as details on when and how they are able to provide both points and miles. You should also check out his double dip booking scenario walkthrough here.
Additionally, PointsHound has a referral program where you can earn 250 miles for each friend you refer who books their first reservation. My link is here and of course feel free to start a conga line with your own links in the comments section.