Check out 10 Tips and Tricks For Taking Screenshots On Your Mac at YouTube for closed captioning and more options.
Here are some of the Terminal commands mentioned:
Get rid of the shadow:
defaults write com.apple.screencapture disable-shadow false; killall SystemUIServer
Change to true to re-enable the shadow.
Change type of file:
defaults write com.apple.screencapture type JPG; killall SystemUIServer
You can use PNG, GIF or PDF as well.
Brilliant information thanks Gary.