Own Text Ad System with Billing?

[quam]

Rather than using a service to deliver ads on my site, I am considering having advertisers input text for their ads, select keywords for the ads, and provide billing information.

Any experience with ad delivery on your own? Is there an open source script that might help (php preferred)?

phpadsnew looks good, except does not include payment by an advertiser. I could do a homebrew script, mainly using insert and select in mysql with php scripts matching keywords with page content --- maybe doing payments through phpCOIN?

[quam]

I'm also looking into the possibility of using shopping cart software like oscommerce and cubecart --- advertisers purchase through the software. Information about their purchase is saved and I can manually add their information to the database with the content.

A bit more work than I planned. The advantage? The shopping cart software includes hooks to payment providers.

Do you or have you had your own 'ad system'? How is it? Any lessons to be learned or suggestions?