Just the links:
GIS represents one of the last great frontiers (along with BI) where the data volume lets everyone work on real computer science. This is a great field, and as long as you are not in europe there is enough public data to make things interesting for the open source developer.
(I actually like any form of programming in the large, distributing computing, design, ...)
Here are a couple of the open source projects I am known to work on:
|uDig||User Friendly Desktop Internet GIS||Architect / Team Lead|
|GeoTools||Geotools - the Java GIS Toolkit||Project Management Commitee|
|GeoServer||the open internet gateway for geographic data||Commiter, focused on WFS-T|
|GeoAPI||OGC Interfaces for interoptability||A Lead, focused usability|