FeedDemon ($29.95) full-featured Windows news aggregator
Bloglines (free) Web-based aggregator
SharpReader (free) simple, well designed, reads RSS and Atom
NewsGator plug-in for Outlook 2000 and newer, online version is free
NetNewsWire ($24.95) well-thought-of Mac RSS reader.
NewsMonster (free or pro) Mozilla browser plug-in supports Linux, Windows
Google Search: News Aggregators.