GeekTool is a nice little prefpane applet that lets you display time-refreshed unix command outputs or Internet-based images on your desktop.
MenuMeters is a great set of system monitoring tools for OSX, displaying CPU, network, and disk utilization in the top menu bar. Sadly, menu real estate is pretty small on my iBook, so I only use it on my G4.
I tried out Bloglines with the OSX notifier, and was less than impressed. I like the persistency of a web-based aggregator, but I hate pretty much everything else. Bloglines doesn’t support importing from OPML, which makes setup a pain, and browsing via a standalone app like NewsFire is much faster [especially if you use keyboard shortcuts].