I know a few friends who are absolute keyboard junkies. They won’t even touch the mouse unless absolutely necessary. I tend to be more pragmatic about my keyboard use. If I use an application a lot, I learn the keyboard shortcuts. Otherwise I just reach for the mouse. That said, here are some keyboard shortcuts that I use regularly. I’ll skip the usual suspects like copy, cut, paste, undo, redo, … 🙂
Windows*
| Close current application | ALT-F4 | 
| Switch tasks | ALT-TAB (2D) Windows-TAB (3D) | 
| Lock your computer | Windows-L | 
| Display task manager | CTRL-SHIFT-Esc | 
| Run | Windows-R | 
| Launch a program in Vista | Windows and start typing | 
| Show desktop | Windows-D (toggles) Windows-M (no toggle) | 
| Go to System Tray (icons beside the clock) | Windows-B | 
| Launch Explorer | Windows-E | 
| Launch application on Quick Launch bar | Windows-1 to Windows-0 | 
| Cycle through task bar | Windows-T – space selects | 
* Most work on Windows XP/Server 2003 and above, though some were added in Vista. So your mileage may vary.
FireFox
| Open a new tab | CTRL-T | 
| Close current tab | CTRL-F4 | 
| Switch tabs | CTRL-TAB (forward) CTRL-SHIFT-TAB (backward) | 
| Re-open last closed tab | CTRL-SHIFT-T | 
| Go to search box | CTRL-K | 
| Go to address bar | CTRL-L | 
| Find | CTRL-F | 
| Go back | ALT-left arrow | 
| Go forward | ALT-right arrow | 
Visual Studio/ReSharper
This deserves a separate post and/or screencast, which I’ll get to eventually. For now, download the ReSharper keymap from here (ReSharper 2.x/IDEA scheme). Personally I wouldn’t bother with the “Visual Studio scheme” for ReSharper. Every ReSharper Jedi I know uses the IDEA scheme.

