Glyn Barnes
What they said.
 
But some people swear by snaggit. It does give more options. Me, i just print screen and crop it MS office photo editor (or Paint).

W7 has the "Snipping Tool" I think ... and it is excellent and probably the one thing I use the most these days!

Most of the time I just hit "Print Screen" and probably shut down the program while the picture is on the clipboard, then get up Paint and Paste from the Clipboard or just Paste.
 
Except in Sonar, if you close down the program after hitting the Print Screen key on the keyboard, you will get nothing to Paste from the clipboard. The only way I found to take a picture in Sonar is to hit the Print Screen key and minimize Sonar to the Taskbar and open up Paint and Paste the image in there and save it first, and then if not doing anything else in Sonar, exit out of the program.
 

I just bring up PhotoShop, Alt-Tab back to the page I want, hit "Print Screen" then Alt-Tab back to PhotoShop, hit Ctrl-N (to create a new document of the same size as whatever is in my clipboard, in this case a screen shot), then hit Ctrl-V to paste it in the new document.  Crop and do whatever, save as a .jpg and I'm done.

Sonar takes up the entire screen (full screen). Otherwise Print Screen is the entire desktop in Windows.

Sonar Exclusive!
 

spacealf
Sonar takes up the entire screen (full screen). Otherwise Print Screen is the entire desktop in Windows.

Sonar Exclusive!
 

Many programs go full screen.  By hitting F11 in Chrome (and the same or similar in other browsers) you can make the Coffee House go full screen too.  The proof is right HERE!

craigb
I just bring up PhotoShop, Alt-Tab back to the page I want, hit "Print Screen" then Alt-Tab back to PhotoShop, hit Ctrl-N (to create a new document of the same size as whatever is in my clipboard, in this case a screen shot), then hit Ctrl-V to paste it in the new document.  Crop and do whatever, save as a .jpg and I'm done.

I click the "Grab" icon in the dock, pick an option (Selection, Window, Screen, Timed Screen) in the capture menu and I'm done.
 

 
I love my Mac. ;)

craigb
I just bring up PhotoShop, Alt-Tab back to the page I want, hit "Print Screen" then Alt-Tab back to PhotoShop, hit Ctrl-N (to create a new document of the same size as whatever is in my clipboard, in this case a screen shot), then hit Ctrl-V to paste it in the new document.  Crop and do whatever, save as a .jpg and I'm done.

Craig, in Photoshop Elements, there is a real neat option to create a new file from whatever image you have on the clipboard:
 

 
@Steve - Yep, PS doesn't have that option (the New dialog goes to a FAR more involved creation window), but just hitting Ctrl-N, Ctrl-V only takes a second anyway - probably faster too! 
 
@Rain - Nice "Grab" you've got there!  LOL! 

An annoying thing is when PrtScn doesn't work because of something else you're doing when you press it. For example, I wanted to harvest a screen shot of the graphical bug which occurs when you drag a clip from one project to another, but I couldn't do it because the thing only occurs before you release the mouse button and PrtScn doesn't register then. I wish it had a timer you could set 

You live and learn - I never knew about the the snip tool. Just pin the icon to the taskbar and its every bit as easy as Rain's discription of the Mac grab tool.