Game engines and tools for developers:

• Devmaster.net – Great list of engines and tools to use
• Blitzbasic – Blitz3D for simple way to create 3D games
• GameProducer.net Tools category – listing some tools for game development.
• GameProducer.net Tool thread – list of low-cost engines and technologies for developers

Game portals and distributors:

• GameProducer.net Portal thread – List of portals and distributors

Art Content Packs

• Frogames – nice looking content packs
• GarageGames Content Packs – optimized for Torque