Thanks to your advice, I installed WP125 and I love it. Calling it an ad manager doesn't do it justice because its functions are not specific to advertising. It can be used to display and rotate any content (images or text with embedded links), schedule their removal from the list and track click-throughs. It does not require a subscription to AdSense or other program to be useful.

If I can be sure that the click-through tracking works correctly, it would be perfect for what I need. Once I generate cash-flow, it is my top plugin donation priority.