How do I toggle on and off sneak in Minecraft?

How can you toggle between sneak and normal standing position? It's kind of annoying having to keep a button pressed while I try to build and move around to get a better view of what I am doing.

While you're holding Shift to sneak, press the Alt key once. This will return control to your mouse pointer, and when you click on the game window again, you will be permanently crouched until you press Shift again.

This only works in windowed mode - there is currently no way to toggle crouch in fullscreen. Notch has, however, expressed interest in adding sneak toggle capability.

I wrote a mod that does Toggle Sneak and MUCH MUCH more, and I plan on keeping it up to date with MC versions.

http://www.minecraftforum.net/topic/355537-166-controlpack-autosneakrunsmartfurnacelookbehindlots-more-v21/