You get what you pay for...Snagit is my vote, for sure!!
Snagit is an incredibally powerful, feature rich, tool for graphics commincation tasks. One of the best parts, for me, is the library of my screen captures. Markup and other editing capabilities are also easy and powerful. Do the 30 day free trial and you'll have no problem spending the $50 for a license.
+1 for Snag-It. As mentioned, the library of captures is very useful.
We also use a template that stamps the image with date/time and throw in a company logo for good measure.