Todd Ditchendorf has released XML Nanny 1.3, a free-as-in-beer Mac OS X program that checks XHTML and XML documents for well-formedness and validity. Mac OS X 10.4 or later is required.
Version 2.0.2014 of Vienna, an open source RSS/Atom client for Mac OS X has been released. This is a bug fix release. This is the first reader I've found acceptable for daily use; not great bit good enough. (Of course my standards for "good enough" are pretty high.) I've also improved the experience a little by installing Feed Your Reader into Firefox so I can now add subscriptions to Vienna directly from Firefox.
