Okay, so we know which projects are picked for Google Summer of Code 2010 now. As you know, one of the points of GSoC is getting new people to free open source projects. Does it actually work?
Here are some interesting facts over the years about organizations that I track to some extent (or even participate at).
Returning students
Inkscape which participates in GSoC since the very beginning (2005) has probably largest amount of returning students:
- Miklós Bálint Erdélyi: Cairo-based PDF export (2006), Poppler-based PDF/AI import (2007),
- Johan Engelen: Live Path Effects (2007), internal paths representation in lib2geom (2008)
- Maximilian Albert: 3D Box tool (2007), Geometric Constructions tool (2008)
- Marco Cecchetti: work on lib2geom features in both 2008 and 2009
- Krzysztof Kosiński: multipath editing (2009, available in upcoming 0.48), Cairo-based rendering (2010)
- Nicholas Bishop: Interactive sculpting with multi-resolution models (2006), Editable topology for multi-resolution meshes (2008), Multi-resolution Improvements (2010)
- André Susano Pinto: ShrinkWrap Modifier (2008), Raytrace Optimization (2009)
- Joshua Leung: Refactor of Non-Linear Animation (NLA) System in Blender for 2.5 (2009), Bullet Construction Toolkit (2010)
Hugin has a returning student Tim Nugent (more below).
Ardour has a returning student Dave Robillard who worked on MIDI tracks support in 2006 and 2007. This work is available in unstable 3.0 branch.
Exchange of students
This year’s Inkscape student Zhengfeng Zhao who will work on Power Stroke LPE successfully completed last year’s brush related GSoC project for GIMP.
This year’s Blender student Nicholas Bishop who will work on multiresolution improvements was Inkscape’s student who implemented UI for SVG filters back in 2007.
In 2007 Paweł Bartkiewicz did a successful project for Mixxx and then a successful project called “Chordata” for CLAM in 2008. Chordata went 1.0 in March 2010.
Students growing to mentors
Hugin/Panotools:
- James Legg successfully completed panorama layout model project in 2009 and is back this year to mentor Darko Makreshanski who will attempt to implement hardware accelerated interactive panorama creation at more steps than just preview.
- Tim Nugent, who did a successful project called Celeste in 2008 and a successful project for automatic lens calibration in 2009, is back as mentor in 2010 for Antoine Deleforge who is about to finish integration of a patent free pipeline for panorama stitching — a work started back in 2007, IIRC.
Inkscape:
- David Yip mentored an Inkboard project in 2006 that he started as a student in 2005.
- Michael Wybrow mentored Arcadie Cracan last year on Connector tool project that he started himself as a student back in 2005.
- Johan Engelen mentors Zhenfeng Zhao (see above) this year after being a student twice in 2007 and 2008 (see above).
As for Blender, Brecht Van Lommel, who did an Inverse Kinematics project in 2005 as a student, came back as mentor in 2007 and never left. This year he’s mentoring the ever-returning student Nicholas Bishop (see above).
Well, like I said, these are just a handful of organizations that I track. If you know more examples, don’t hesitate to tell 
There is one thing about GSoC, however, that I absolutely dislike, and it’s Melange — the new web engine behind GSoC’s website. Up till 2009 finding what projects had what students was a no-brainer job. With introduction of Melange, however, navigating GSoC’s website has become a complete disaster. It has been reported already, yet nothing was ever done about it. I very much hope that Google will either revisit this decision or fix the usability issues pointed out.