I take a lot screen shots. Every day. In the bad old PC days, it involved hitting the prnscrn key, pasting into Word or Photoshop, etc etc. When I moved to the Mac it got easier, with some short-cut keys. But I still had to do the Photoshop thing if I wanted to annotate or add arrows or such.
Yesterday Bradley pointed me to Little Snapper, a new (?) app for the Mac. I won't event try to list or describe the features in LittleSnapper, there are just too many. But if you're a designer, developer, researcher or writer, you'll want this on your utility belt.
At $39, this is probably not a tool that everyone needs. But if you use screen grabs as much as I do, it's a must.