I'm interested in hearing what others have to say, since I got mine just last week!
Blockbuster credited quickly (and it's one that I really wanted to try, anyway!). It costs 9.99 (and tax), but paid 29 last week when I did it. They will also put a hold on the next month's subscription of 9.99 (so it will tie up some of your money).
Cinemanow was a quick credit, and easy to cancel, but beware, as they placed a hold on a month's subscription (I think many places do this, btw....which I think was $29.99 ish), so that money was tied up for about 5 days, and then it was released, after I cancelled it.
Efax credited quickly, and I'm going to try to cancel it this week (I wanted to try this one, too). I've heard you can cancel this one online.
Oh!! The business AMEX is a high payer, IF you really do have a side business-they DO ask all kinds of questions when you activate it, at least they did for me. I have a "work from home, catalogue/party" type business that I've been meaning to have a credit card for, so that worked out nicely.
Did you see the thread somewhere on this board (sorry...kids are yelling, I have no time to find it) that talks about which offers can be cancelled ONLINE??? It was a help for me to decide my first few....until I'm more confident!
I'm about to try a few more, but since I only had $75 on my card, and so much of it got tied up with these offers, I've been waiting the past few days until the money was freed up again
GOOD LUCK!!