NewsGator offers several free RSS aggregators for the Web, desktop, mobile devices and e-mail clients, as well as a number of for-fee services available to help enterprises and media companies leverage social computing solutions.
A version for Windows, Mac, and iPhone. FeedDemon for Windows; NetNewswire for MAC and iPhone. Includes Widgets, search engines, 3rd party add-ons, etc.
Free. Premium for iPhone, no add ons is $4.99 and $9.99 for iPads: http://www.newsgator.com/rss-readers.aspx