My first instinct at seeing your message was to point you at SQL-Ledger, which is written in perl as a web application. It is designed to be more of general accounting package but undoubtedly has a lot of what you are looking for already built.
But after rereading your message I think you should look at using the Mozilla platform. There is a slowly growing group of people using Mozilla for application interfaces (even the US Navy). Combining it with a small lightweight httpd (e.g.
tinyweb,
Jetty (300K java httpd
)would probably work (Updated: added webserver links). Here are some articles about it if you wish to pursue this course:
