[MrMike]

Same amount to each recipient each month?

If you're with a major bank (BOFA, WF, etc), you can schedule payments with your bank via their online banking.

The original question implied an API for outgoing payments, but since that doesn't exist (afaik), you can ease the burden. For payments that vary in amount, most major banks allow you to add a payee once, then whenever you know the amount/date a payment will be due, you can schedule it. Ideal? Probably not, but I find it much less painful than checks+stamps+USPS.