There are a few select things I will purchase, and mostly through MyPoints.
I always get the boys' contacts through 1-800-Contacts/MyPoints. At 750 points for a $19.95 purchase of one box. (That offer is good once a month) (I buy the left eye one month, the right eye, the next month, then do the other kid, etc., etc.) That's hard to beat. (I also get reimbursed for that $19.95 from insurance).
When the boys need cleats or baseball stuff, I always buy that through footlocker.com or sportsauthority.com and MyPoints.
I have also had some good success signing up and cancelling, Connections, Simple Escapes, 24 Protect Plus, and HomeWorks Plus. In addition to the points, I got a $25 Borders/Waldenbooks giftcard, a $50 Wal-Mart card, a $25 Kmart card, and a $25 Home Depot card.
On the Borders/Waldenbooks card, I bought the 2003 Unnoficial Guide. On the other cards, I used them to buy stuff we would need anyway, and then used an equivalent amount of cash to purchase Disney Dollars.
Hope this helps.