Well, you're lucky cos you're in the US so have many more options than we do in the UK where the banking system has get very tight with merchant acquirer accounts over the last 3 years. We have to have been trading for 2 years now before they will issue an account - makes it very difficult for a new start-up even if it is a limited company and the people involved have excellent track records in business.
I came across Google Checkout the other day which is advertising FREE transactions for 2007. Only available in the USA for now. Their normal rates are far better than PayPal's anyway, but free is better than anything. Not looked into all the features cos I'm in the UK, but being Google I'm sure they have all the features that other providers have.
Otherwise, if you use accounting software like Quickbooks then it is probably integrated with payment processing - again only in the US - and you can then use your accounts package to handle subscriptions and repeat billings.
If you have a merchant account then I can only recommend SECPay . Used them since 2001 and they are excellent: easy to integrate, fully documented API, personalised pages on their secure server and very competitive charges.