There's https://www.bestegg.com too, they send me like 1 mailing a week and I get mailings from other very similar companies, as well as established banks, several times a week.

I do not know if it's a saturated market yet but it sure seems like it.

I currently have ~$10,000 in credit card debt at 0% interest, no I don't want to refinance that, thank you! (I got the money sitting in a CD when the interest free period runs out.)