AlphaGem is a desktop podcatcher written in C++ and Qt. Most desktop podcatchers are web-based and therefore don't support offline playback, or are general-purpose media players that support podcasts as an afterthought. AlphaGem is a dedicated podcatcher with a user experience and featureset to reflect that, including automatic refresh and downloading, download pausing and resumption, playlists, feed content (e.g. episode descriptions and transcripts) and more.
AlphaGem has been released under the zlib open source licence and is available on Github.