If you are using Twitter and looking for a desktop tool, take a look at TweetDeck. It's in beta, it's free and it's available for both mac and windows.

The interface can be used as a simple 1 column feed and tweeter or you can customize it to include groups of friends, Facebook Status, Direct Messages and include several columns of information based on the size of your monitor and your needs.

http://www.tweetdeck.com/
 
For a quick tutorial, check out this getting started video by Cali Lewis/Geekbrief.tv http://www.geekbrief.tv/gbtv-517-how-to-tweetdeck-like-a-pro.>

I've been using the Jing application on a mac and pc for several months now. They have had several updates and if you installed the original version last year, you should download and reinstall because the original version, at least on the mac, did not auto-check for updates. The latest rev has several bug fixes and refinements in its interface. Jing can auto start and be available with a click of a button or by a keyboard shortcut. What's great about Jing is you can select to grab the entire screen or a portion of the screen as a still or as a video. Looking at the still grabs you can easily annotate with text, add arrows or highlights which makes it a great for bug recording or pointing out parts of graphics that you need your team to address, adjust or work on. The video tool allows you to easily save a screencast to share with a client or friend and either post, email or use the Jingproject.com site to instantly share via a link. Strongly recommend adding this free tool to your toolset and taking advantage of its features. Jing now offers a pro version to enable better video compress plus several additional Pro features. Jing was created by Techsmith.com which has several great windows products including Camatasia, Snagit, Morae, and Uservue.

Example of a marked up screen: