I'm a huge fan of Beagle Brothers style cheat sheets, because nothing promotes the illusion of mastery like a densely packed chart of obscure reference information:

Just throw some of those babies up on your walls and people will know that they're clearly dealing with a coding genius!

VisiBone makes great modern equivalents of these classic references, and they're available in dense card, dense foldout, large print book, and huge wall chart formats. The Visibone regular expression reference is the best concise regex reference I've found to date -- and there's a free online version, too. It is limited to the JavaScript regex syntax, but that's 98 percent of what most people will need.

I've seen the CSS Cheat Sheet before, but I didn't realize there's an entire set of cheatsheets freely available from the same site:

• ASP/VBscript
• HTML Character Entities
• JavaScript
• MySQL
• Apache mod_rewrite
• CSS
• PHP
• RGB Hex Color

These are all conveniently provided in PDF or PNG formats. If you're a Microsoft .NET programmer, there's no shortage of cheatsheets for you as well:

• Visual Basic 2005 Keyboard Reference
• Visual C# 2005 Keyboard Reference
• Visual C++ Keyboard Reference
• Format String
• ASP.NET 2.0 Page Lifecycle and Events
• Visual Studio 2005 C# code snippets

If you don't see the one you want, here are few other sites that aggregate cheatsheets. Many of them are open-source / UNIX oriented, but they run the gamut.

• Dr. Web's Cheat Sheet List
• Bluewin's Cheatsheet Sites

Know of any other good cheatsheets not listed here? Share in the comments!