Over the past 10 years, I have dabbled in many "miscellaneous" frequent flyer programs and have actually earned awards out of some.
One of the oddest ones for me was Grupo Taca. I once had a website with referral links that earned me miles with them. Well, I eventually earned enough for a free trip to Panama. ^
I also participated in AirTran's program simply to take advantage of the Wendy's promo two years ago and earned a free trip to Las Vegas.
I recently signed up for an account with BMI when they topped off the account with 9,000 miles; enough for a Zone 1 aware. I have not used it yet (+ 2 other family member accounts) but I haven't forgotten about it either!