Is there a free program that allows me to take a snapshot of whatever is on my computer screen?

first of all, which OS ?

Applications/Utilities/Grab

You’re on a Mac?
Press command+shift+3.
If that doesn’t work, open up a utility called Grab. It’ll do your trick, and it’s included with Mac OS X

if you’re on Windows OS I know you could just press Print Pg key with Ctrl and than paste on any Word doc.

skitch is a cool program too

http://skitch.com/

In addition to what lefteh said…

If you want to take only a portion of your screen, press command + shift + 4.

Or Cmd+shift+4 then spacebar to select a whole window

For anyone interested in a Windows answer…

- The PrntScrn button will copy a snapshot of the entire screen to the clipboard.
– Ctrl-PrntScrn will copy a snapshot of the current window to the clipboard.

In Vista, there’s a program called ‘Snipping Tool’ that comes with the OS – just search through your start menu looker…
You know, the spotlight rip-off. Yeah, that’s it.

There is something intensely comedic in using the Spotlight rip-off to find the Grab rip-off.

Hahaha, to be fair I’d never heard of Grab, I usually use CMD+SHIFT+4 with all the nifty shift/alt/space modifiers…

@benseven, the cmd+shift+4 is a just a shortcut for grab, i believe, but it doesnt open grab, it just takes the shot

If we’re going to give answers for other operating systems…

For those interested in the Xubuntu and Ubuntu ways, press PrtSc for a screenshot of the whole window and Alt+PrtSc for a screenshot of the current window. You can also open up the Gimp or install ksnapshot for more advanced options.

So, anybody willing to name all other operating systems in the world? ;-)

Snagit is also an excellent program. I miss it, actually, as its not available for mac.

faststone image capture is excellent – it captures images, video, it can scroll a webpage or document so it can grab everything in one image even if it does fit on your screen. You can also capture just an area of the screen. Has lots of output options but not sure about PDF. You can of course convert the images it creates into a PDF later.

It’s not free but it has a 30 day trial and then it’s only $20 if you want to keep it.

I second @stocky, www.skitch.com is one of the coolest programs i’ve ever seen