Frugal Travel Guy walks through in some detail the process of buying grocery store money orders with credit cards for the points, depositing the money orders in your checking account, and using the funds to pay off the credit card. Rinse, repeat. A definite must-read!
Meanwhile, I haven’t played around with this myself, but he also writes about $250 all-in fares to London (using Priceline and clicking through various flight options) and 250 free Delta miles for signing up for their online mall. Note that I haven’t seen anything myself about the 250 bonus miles, no email in my inbox and nothing on the website, so that one may well be ‘your mileage may vary’.