[slig]

If you're on a Mac, try Command + Shift + 4 to take a screenshot with a crop tool that's saved on your ~/Desktop folder.

[indubitable]

The Windows equivalent (it sounds like) is Snipping Tool. Start -> Snip will show it. Or you can navigate to it under accessories. Extremely handy.

[nerfhammer]

try command + cntrl + shift + 4.

copies the image straight into the clipboard, no detritus to your desktop. many web apps will just accept the cmd +V paste like an uploaded file.