I received an email from UAL Milage Plus - Quoted below. Very easy to get those 7500 miles - Office Depot is a merchant on the milageplus mall - all shipping is free - so buy the cheapest item. 1 activity gives you 2500 miles. Find a milage plus dining restaurant -buy something cheap -even fries :-) and you have completed tow activities as required - for a total of 7500 bonus miles.
---------EMAIL QUOTE--------
" Give yourself a gift of up to 7,500 bonus miles this holiday season. Through December 31, you'll earn 2,500 bonus miles when you complete one of the following four activities. Complete two of the following and earn 7,500 bonus miles!*

Purchase and complete a qualifying United flight

Shop the Mileage Plus Mall for last-minute gifts

Enjoy a holiday meal at a participating Mileage Plus DiningSM restaurant

Stay at one of our partner hotels
Hurry, this offer is valid only through December 31, 2003!
Happy Holidays from Mileage Plus!"