Indispensable Computer Graphics Sites

1. Google Scholar for finding papers, Google Groups (comp.graphics.algorithms), and Google - they're not graphics specific, but are infinitely useful.
2. NVIDIA and ATI developer sites - demos, code samples, white papers, etc.
3. DevMaster.net, GameDev.net, OpenGL.org, FlipCode (closed, but good archives) - Daily news, more tutorials and samples, and cool stuff.
4. IntroGameDev and AI Wisdom are excellent guides to articles in Gamasutra, Game Developer, and all the major book series (GPU Gems, Game Programming Gems, and ShaderX). IntroGameDev is more comprehensive, but AI Wisdom includes abstracts and other information.
5. GPGPU.org - all about using the GPU for general purpose computation, the site also has useful info about GPU programming in general in their FAQ, wiki, and throughout the site.
6. GRAPHBIB - freely search a nearly complete set of references to computer graphics related research.
7. Ke-Sen Huang's resources page has links for papers from all the major computer graphics conferences and workshops. Frédo Durand's page has links to researchers, labs, publications, and more.
8. Graphics Gems Repository - contains the source code for many graphics algorithms. Search the contents by category, by author, or by book.
9. Geometric Tools - there are many different code snippets and tutorials here to do all sorts of graphics operations, with a focus on computational geometry and intersection methods.
10. Sourceforge is the best place to search for free, open-source software applications.
11. FAQs - useful, condensed information on many aspects of computer graphics. Particularly valuable is the comp.graphics.algorithms FAQ, maintained by Joseph O'Rourke.
12. journal of graphics tools - a small but useful repository, as many of the articles have code associated with them, freely available for download.
13. 3D Engines database - a browser for 200+ rendering engines. If you're looking for code for most any real-time rendering method, it's probably listed here. Also see the 3D Engines List for a much older list, but one with some software renderers that may be of interest.
14. OpenGL Reference - a nice site with OpenGL 1.3 and WGL man pages hyperlinked. The new proposed OpenGL 2.0 specification papers are also linked from here.
15. NPR Survey - a great collection of links to Non-Photorealistic Rendering articles, demos, etc.
16. 3D Object Intersection Page - where to find articles and code on this topic.
17. Eric Weisstein's World of Mathematics is an incredible resource for mathematical definitions, hopefully back on the web for good.
18. Graphics Accelerator Reviews - try Tom's Hardware Guide, AnandTech, Sharky Extreme, [H]ARD|OCP, HotHardware, Beyond 3D, FastGraphics, Tweak3D, Björn's 3D World, FiringSquad, and Hardware Central, in more or less that order.
19. Game Developer source code archive - I do not visit this one frequently, but it is one of the first places I look for demos and sample code for purely real-time related graphics algorithms. Others include
20. Gamasutra's programming page - it's a place to start learning about a topic, try a demo, and find some sample code.
21. ACM TOG software and literature links pages - links to source code, papers, tutorials, etc. The 3D model section is particularly useful.
22. Real-Time Rendering links page - how self-referential! But I do use it a lot. Don't forget the mirror.