In the last weeks I have been working on a new program called Milkshake. It is primarily a To Do list organizer but we want to promote Milkshake a little bit more. Milkshake has a plugin architecture and it is simple to create extensions for importing/exporting/sync the task lists. At this moment, my friend javsmo is working on a plugin for Remember The Milk that will allow real synchronism with external sites and I wrote some basic plugins for backup (import/export) (I will write an article about plugins in PyS60 and post it at FN wiki soon).
I would like to invite you to test Milkshake and, who knows, to write a new plugin. For instance, it is possible to write a plugin to sync with google agenda or with some bug tracking system. Just ideas, feel free to comment and share it.
The current recommend version is 0.1.0 (for Python 1.9.6), available at google code under branch 0.1. Plugins initial documentation is at this page and screenshots at this page.