Audio
  Plasmatweeter (german only)
IN-33 Plasma Bargraph
TPA0212 Headphone Amplifier
Philips SAA70xx (CD-104) SPDIF addon
Photography stuff (mods, addons, ...)
 

Infrared only conversion of Sony Cybershot P71
Remote Control for Olympus E-Series offering many different shoot modes, interval, bulb timer, ...
Laser Autofocus Illuminator
Amateur Radio

2m stuff:

 

 

 PIN-Switch (ger.)
Omron-Koaxrelais (ger.)
High Power PIN-Switch for VHF Amplifiers
145 MHz low-pass filter for power amps
145 MHz solid state 400 Watts amplifier (Semelab D1030UK power FET)

13cm stuff:

 13cm 1W power amplifier with 20dB gain

Other:

 A Versatile 25MHz AD9832 DDS Synthesizer
Others
 

Modded 12V Camping Cooling Box WATER COOLED
PS/2 keyboard Infrared Interface for WDTV Media Players