audio software
KVR Audio
Rekkerd.org
db-audioware
sonic timeworks
TC|Works
Adobe Audition
Steinberg
Tracktion
Ableton
Samplitude
Tobybear VST plugins
KeyToSound
Rob Papen - Inspiration Soundware
Native Instruments
Koblo
Musicrow - Reaktor Ensembles & VSTi

 
drums
Drummer World
Sinus' virtual drums
Tomas Howie Drum Web
drumbum
Marco Minnemann
Mike Portnoy
Steve Alan
Joe Babiak
Vic Virth - Drum Corps International
Mr. Bean and the Invisible Drums

 
sounds
Loops4free.net
freshloops.com - Download loops legal for commercial production at FreshLoops
samplecraze.com - SoundFont developers / LICENCE FREE sample cds
mpc-tutor.com - Akai MPC Sounds & Samples
mpc-samples.com - Akai MPC Sounds & Samples / tutorial books
breakbeatvault.com - vinyl breakbeats and raw hip hop drum loops

dsp
DSP Links
Harmony Central - Audio Programming