Sometimes I want to make a picture of my computer screen and share it in my blog or in my social networks.  I really like jing.com for that purpose.  Once you download it, it sits on top of your screen as a half circle that activates when you put the mouse over it.  You can select which part of the screen you want to capture.  Then, you can then make a picture or a video from your selection (in the pro version, you can also record from a webcam).  The next step is to name your recording.  After that, you can decide if you just want to save the screenshot, want to share it via screencast.com, copy it or edit it in Snagit.  Snagit does not come with Jing, you would have to purchase that separately.  The best thing about Jing is that it is for free as long as you use the basic version (without the webcam option).  Here is an example of my post: