EFS processors work. Sportsbook.com and Betmania accept them, at least the All-Access Gift cards and prepaid ones work.
Here you can find where they sell them at:
www.netspend.com (this is for the permanent type- they will send you a card in the mail with your name on it)
www.allaccessgift.com (this is no-name, just the temp card- you cant reload this one)
Dont forget if your (permanent) card has a fee for purchases, that you figure this fee in when you send money to a book, or it will be declined for going over your card balance. On the all-access gift card (temporary card) there is no fee.