Jennifer makes an observation that she'd like to see a collaborative online scheduling service that supports a customers ability to make appointments online with the business owners ability to publish available dates, times, and resources.

Funny you should mention this Jennifer, as I was just contemplating this service myself. In addition, I think the service should send automated appointment reminders. I know my Dentist and Accountant could use such a service as "no shows" cost them money.

All of the basic components are available to do this (we did something similar a couple years ago for a Healthcare Patient Self-Service Portal). Maybe it's time to seriously revisit this solution within a Salesforce.com context?