RocketMiles is a hotel booking service that awards airline miles for hotel stays. They have had similar bonus miles offers with number of airlines and United previously.
Note that you must choose between any one first time booking offer. You cannot do both the 5,000 and 3,000 bonus points ones.
If you choose your hotel carefully, the miles that you get from your first hotel booking using RocketMiles can pay for the stay.
Here are the terms and conditions of this offer:
To be eligible for this promotion, a hotel reservation for at least three (3) consecutive nights must be booked using this promotional link (www.rocketmiles.com/united-5k-bonus) by 11:59PM CT on 30 November 2014 and check-out must occur by 28 February 2015. Limited to first time customers and subject to investigation post-purchase. Limit one per customer. Limit one per stay. Promotional offer cannot be applied to existing bookings or retroactively applied to bookings not made using the link above. This promotional offer cannot be combined with any other offers, including a sign-up from referral bonus. Rocketmiles reserves the right to retract a bonus at any time if it detects technical errors, cancel/rebooking activity (defined by identical search criteria), or any deceptive behavior attempted to circumvent the limits expressed above, including multiple accounts. Please allow 2 weeks for bonus miles to post in a qualifying member’s account after hotel stay is completed and the qualifying member has met the stated conditions.