Benjamin Pasero has released of RSSOwl 1.1.3, an open source RSS reader written in Java and based on the SWT toolkit. Version 1.13 fixes various bugs, shows the number of unread items in each channel next to the name, supports drag and drop, and add the feed protocol. RSSOwl is the best open source RSS client I've seen written in Java. That said, it still doesn't feel right to me. Even ignoring various small bugs and user interface inconsistencies, news just doesn't flow in this client. The three-pane layout that separates the news item titles from each news item doesn't work well for me.
Ranchero has released NetNewsWire 2.0.1, a closed source RSS client for the Mac. It's available in both free-beer lite and $25 payware versions. Version 2.0.1 adds support for Atom 1.0 and fixes a few assorted bugs.
The Omni Group has released OmniWeb 5.1.1, a $29.95 payware web browser for Mac OS X. OmniWeb 5.x is based on the same KHTML engine Safari uses. However, it has much less XML support; in effect none. It seems to believe that all XML documents should be RSS and gets very confused when they aren't. This is one of the most XML-hostile browsers I've seen in years. Give it a pass.