• Using OpenOffice.org 3.x: e.g., a good introduction to OOo Impress or mail merge.
• Maul Publisher: Creating sophisticated layouts.
• Video encoding: How to create videos of the Matroska (MKV) container format with several audio and subtitle tracks. This should cover using x264 video, AAC and AC3 audio, and srt and ssa subtitle formats at least.
• Using Samba in heterogeneous networks with Linux, Windows, and Mac OS X. Should cover both client and server.
• Development with Qt 4: porting existing and writing new apps.
• Surf Stick (UMTS / HSDPA) installation and usage
• Your suggestion

You may also want to have a look at the previous WishListForWarpstockEurope2009|wishlist for Warpstock Europe 2010.