ASP.NET

• MS Ajax Library (aspnetresources.com)

GIMP

• GIMP command reference @planetozh.com

Google

• Google sites & services @ http://www.feedsforme.com/google/

Ruby on Rails

• InVisible Ruby On Rails Reference 1.1.2 in HTML and PDF formats

Subversion (SVN)

• Cheat sheet from abbeyworkshop.com

Visual Studio.NET

• Visual Studio .NET 2005 Keyboard Shortcuts
• Visual Studio .NET 2003 Keyboard Shortcuts

Yahoo

• Yahoo UI (YUI) controls cheat sheet

Collections

• digilife.be – lots of quick references in PDF format on Ada, Delphi, C, C++, C#, CVS, Java, Perl, PHP, Python, Linix, Ruby, SVN, SQL, UML, Unix, VB.NET and XML
• techcheatsheets.com – cheat sheets with tags and rating system