The links lead you to the thread on GTAforums right now. I hope to make this list more complete and link to screenshots where possible in the future.
My Workshop - Various things I've done
SkyGFX (III/VC/SA) - PS2, XBox and partly Mobile graphics for PC.
Sharptrails (III/VC) - Reimplementation of the trails effect but without blur.
Skin & Bones aka. iii_anim (III) - Skinned animation from Xbox/Mobile for PC.
Debug menu (III/VC/SA) - A DLL that lets you change variables and call functions from within the game at runtime. Also comes with a debug plugin that uses it for various useful stuff.
LC98 (III) - Brings the atmosphere of LCS to III. Still the same III but now looking like LCS.
Beta Infernus, Phoenix and Police car (VC) - My attempt at recreating some VC beta vehicles. The Infernus turned out really well. The Phoenix and Police car are older but not too bad either.
In-game Timecycle editor (III) - This grew out of my work on GTA3D.
24h Timecycle (SA) - Extends the Timecycle from 8 to 24 hours. Originally grew out of my work on VCSPC.
Real time clock (III/VC/SA) - Syncs the in-game time with your current local time.
rwd3d9 (III/VC) - A dll that extends RW for d3d8 with d3d9 functions, needs a d3d8to9 wrapper. Used by SkyGFX and sharptrails.
Simple DLL Loader (III/VC/SA)
- Yet another
ASI DLL-loader. I got fed up with abusing the ASI extensions and having
loaders automatically load my files. With this you get more control over you plugins.
Simple Screenshot Plugin (III/VC/SA) - Makes screenshots
PS2 and XBox vehicles for PC (III/VC/SA)
- Straight conversions of the vehicles from PS2 SA and VC, XBox VC and III.
SA's PC vehicles are somewhat bugged, PS2 are better. VC's PS2 vehicles have higher reflection coefficients.
III and VC Xbox vehicles are improved versions of the PC/PS2 models.
RW tools - Converter between various RW file formats.
rwio - An importer and exporter of dff files for 3ds max. Certainly not perfect but better than KAM's scripts in some ways.
Track and Path editor for 3ds max - A small MAXscript tool to edit train tracks and flight paths. Grew out of work on GTA3D.