I use this:
The Coupon WalletŪ Organizer! - www.TheCouponWallet.com
I bought it off Ebay for $15. It paid for itself within a month or two. The only problem with it was that I don't buy a lot of food that has coupons (it is usually boxed foods and such, which we don't buy a lot of), so I would end up with half the slots empty and 100 coupons for toiletries all mashed in together. To solve that problem, I got rid of their index tabs and made my own.