Seeking guidance on how to add users location in Drupal 6

Hi,

I'm trying to use Drupal 6 as back-end for a map web application that show "ubuntu supporters" in Belgium (see http://map.ubuntu-be.org) and need guidance. The plan is to store user location and their commitments in Drupal. Then the existing JavaScript could be refactored to fetch the data from Drupal instead of the current had-hoc backend. After some research, it seems that the best solution to add (optional) information to user profile is to the Content Profile to create a "Profile node" for volunteering users. This node would have to provides a means to store user location.

So what I need is
1. Store the addresses (a) and lat/long (b) of the user in the node.
2. Retrieve the list of all users in a JavaScript parsable way (JSON, XML or even plain XHTML with microformats) filtered by some fields (not the location themself).
3. Optionaly, refine 2. so that users can be searched by location too.

Point 1.a can easily be done in a ''profile node'' using the Addresses module. For point 2. there seems to be some possibility with the Services modules but it clearly depends on the feature provided by the modules used to achieve the first point. Point 3 can wait, the only requirements is that the solutions for 1 and 2 must be not lead to at dead end regarding this goal.

So I'm currently searching a clean solution for 1.a as I did not found any module that let me store the lat/long (I'm working with Drupal 6). The only solution I see is to develop may own little module to store the lat/long (either as an Addresses extension or as a simple CCK module). But it seems like a waste of time (and I don't know a lot about Drupal development, I'll have to learn). I would better use the little time I have contributing to a widely used module. I don't have a lot of time, nor does I have experience with Drupal, but I'm pretty experienced with PHP and JavaScript.

Does any one see where I can help and contribute while also working towards my goal ?