Some Examples

Bdale Garbee, KB0G
Antenna tracking, AO-40 telemetry, "Everything!"

John Ackermann, N8UR
Debian/KDE/Openoffice.org laptop used for presentations, APRS
Jaye Inabnit, KE6SLS
SSTV, PSK-31, etc
Peter Lemken, DF5JT
XPlanet
Joop Stakenborg, PA3ABA
logging, dx-cluster

Joaquin Seoane
Health and welfare networks using Debian and AX.25 links!
http://www.ehas.org