"Seriously Instant Screen-Grabbing" Gyazo
Gyazo uploads a screenshot to a to the Gyazo website after the screen area to be grabbed has been selected. From there you can reference the URL:
or post the image on to the image hosting stie of your choice.
Upsides: Very quick, free.
Downside: Gyazo hosted images are read only and cannot be deleted once uploaded [for now]
Link: Welcome to Gyazo | Seriously Instant Screen-Grabbing
[Careful putting the URL in: I am a little tired tonight and I entered a typo which led me to a website which was definitely not to my taste]