Using a PC I always used a program to capture my screenshots. With Mac's it is so easy now to do just the same... and you don't even need to use a program to do it...
Command+Shift+3
Capture entire screen and save as a file
Command+Control+Shift+3
Capture entire screen and copy to the clipboard
Command+Shift+4
Capture dragged area and save as a file
Command+Control+Shift+4
Capture dragged area and copy to the clipboard
Command+Shift+4 then Space bar
Capture a window, menu, desktop icon, or the menu bar and save as a file
Command+Control+Shift+4 then Space bar
Capture a window, menu, desktop icon, or the menu bar and copy to the clipboard
O'Reilly -- Mac OS X Screenshot Secrets