Quick reminder, United has double EQM miles if you sign up by April 21. Also, if you use the "Mileage Plus Mall":http://mponlinemallcom and use it to buy from Apple, you get one mile for each dollar on top of what your credit card gives you.
For instance, with "Hertz":http://offer.hertz.com/offers/index.jsp?targetPage=uaelite.jsp?id=5964 if you use the Mileage Plus discount number PC62455, you can earn 1,000 bonus miles on a 2-4 day rental
The "Avis":http://www.avis.com/AvisWeb/html/partner/ua/elite.html?ICID=PartnerUA&IID=elite2008 promotion is not as good. It is 250 bonus miles for 3-4 day rentals. The discount number is AWD K019300