Refractions Research has joined the Google "Summer of Code" as a mentoring organization. That means we are hoping to get some great proposals from students looking to enhance PostGIS as a "Summer of Code" project.
If you are a student, check out the ideas page for what we have already brain-stormed as potential projects. If you just have an idea for a Summer of Code project, raise it on the postgis-users mailing list.
We are looking for good projects that will help move the project forward, but can be realistically completed within the course of a summer.