How do you handle direct ad sales?
apowell: Set up recurring billing, don't chase checks every month.  Send invoices if it makes you and/or the client happy, but collect the payment automatically.  I use Authorize.net for billing and Blinksale for invoicing.This will save major headaches and improve long-term advertiser retention.  (And if your advertisers aren't long-term, I suspect you'll have a tough time continually generating the new accounts necessary to make this worthwhile.)