S.B.
Michelle - if you don't already have a 529 for your kids, then this is a way to do it. I have been a member of Upromise since before my son is born, he's now 2 1/2, and I have earned a total of about 60 bucks. But this is because I do not shop at grocery stores, really, I shop at Target, Sams Club, etc., which don't participate. When I order online stuff, I look and see if they have it first. You could probably make good money if you really worked it.
They now link to a 529 plan - the Vanguard (which is decent - a 529 is new enough that there is not alot of historical data to compare), so once a quarter, it dumps my earnings (if they're over $25) into my 529. The 529 is an automatic savings - you sign up to have x dollars transferred into it per month - I think the minimum is $50.
So if you plan on doing a 529, then Upromise/Vanguard is as good as any. If Upromise didn't link to a 529, though, I doubt I would use it. The rules are really hard to pull your money out.
It doesn't cost anything to sign up, so you might as well try it for a few months and see what you can do with it.
Good luck!
S.