Scott,
You may want to check out Vanguard Airlines. First of all, they usually have some cheap flights (current prices are $89 each way from Denver to Chicago Midway, but prior to the gas hike I was seeing promo fares for almost half that). In addition, for booking online (flyvanguard.com), you can earn a free ticket on Vangard (they also go to KC, Myrtle Beach, ATL, PIT, Buffalo, DallasFW and CIN.) after only four round-trips. They fly Boeing 737s.

If you're looking for free flights without travelling, try the MCI and Sprint offers (go to the respective forums on this site and check the last 10-20 days) and/or do credit card promos, which can net you 5,000-10,000 miles for Amex/Visa, and up to 24,000 miles for Diners [$80 fee, 12,000 miles without double promos). The closest thing running to the pudding scene is Diet Coke (dietcokerewards.com), which can allow you to rack up to 25,000 miles on Delta (this may expire in April) for consuming 67 cases of diet coke. Through the credit card, phone and mypoints deals, I've accumulated approx. 150,000 miles on various airlines while flying only about 5,000