- RCX Subforum on LUGNET
- r/mindstorms: General to Lego MindStorms, but does include some RCX topics
- “Bricks” StackExchange: General to Lego, but does include some RCX discussion
- EuroBricks: A portal for LEGO fans to share their creations, discuss LEGO themes, participate in contests and challenges, and join the community.
- BrickLink: A marketplace for buying and selling LEGO sets and parts
- Virtual LEGO building software
- From LEGO: LEGO Digital Designer
- Third-party, Freeware, and Open Source:
- LDraw.org: A system of free software tools for modeling Lego creations in 3D on a computer
- LeoCAD: A CAD program for creating virtual LEGO models (also included with the LDraw All-In-One-Installer)
- LPub3D: A WYSIWYG editing application for creating LEGO-style digital building instructions (also included with the LDraw All-In-One-Installer)
- …and more: Visit this LDraw page for more software listings!
- Archive of official software shipped with various LEGO sets: Brick Factory