Karrigell is too complex for my needs. I'm going with mod_python for the web service backend and PHP/JavaScript for the frontend.
Going with PHP for the backend would make it easier to move to an external server that might not have Python, but starting with Python allows a quick start and giving some KPA-MySQL access code back.
The Publisher mod_python handler is excellent, exposes functions with their parameters. Extremely easy for web services. Combined with JSON for transfer of data, the web service side of it is pretty much taken care of.
The trick now is the right division of labor between PHP and Javascript. Unfortunately, there's not a lot of obvious tutorial for Prototype.