FeedFlow is a sidebar gadget, allows you to read the feeds you want easily. It will not use much of system resources whilst allowing you to read RSS and Atom feeds easily.
FeedFlow Features:
1. You can hide the feed items you have read.
2. You can filter the parts of your feeds separately, you can prevent seeing particular items by their title or by their content.
3. You can resize the gadget dynamically, without opening the settings. It will automatically adjust the number of feeds per page according to the height.
4. You can set your own font and font size.
5. You can set autoscroll interval and it will automatically change pages.
6. You can easily create your own themes.
7. You can view feed thumbnails when you click on feeds for details.
8. Auto-update will mostly take care of the bugs & improvements, you only need to install the gadget once.

The license of this software is Free, you can free download and free use this rss reader software.