The 2006 Linux Kernel Summit

Here's how to fix the picture in a few easy steps

1. Open it up in the GIMP
2. Select Layer->Colors->Levels
3. In the dialog that appears click the eye-dropper button on the bottom right of the dialog: it should be to the right of two other eye-dropper buttons and an "Auto" button
4. With the eye-dropper, click on a part of the image that should be white (one of the T-shirts would be a good candidate). Click on the brightest spot
5. As soon as you click the change should be visible
6. If you're feeling adventurous, you can click on the middle of the three eye-droppers and select a part of the image that should be grey, but this is a bit harder to get right
7. Make sure to click OK in the dialog when you're finished, otherwise your changes will be discarded.
8. For last minute tweaking, select Layer->Colors->Brightness-Contrast and muck about with those a bit.

The resulting image should look a lot better, though there may be some speckling (this is why pros use the Curves dialog). Here's my attempt: http://www.bfeeney.uklinux.net/images/group.jpg.

There's a good guide to this stuff at http://arstechnica.com/guides/tweaks/mystery.ars.