500 FREE & 1,000 Bonus miles after registration and & purchase ($25) with mypoints
United Mileage Plus just sent out an offer
to register for mypoints.com that earns 500 miles.
It does not seem targeted.
If you manage to buy $25 or more in the first 30 days – you will receive an additional 1,000 miles.
This list will show what merchants offer (sorted by the highest offer, which works only after you are registered).
Interesting merchant offers include Aeropostale (10x) and Sears (9x). Gift Cards usually post points with Sears but it may not with mypoints purchases.