One thing I wanted to do for a long time, but wasn't possible until GObject introspection (short GIR) came around, was a playing multimedia attachments from within Liferea. Maybe you remember how we sometime ago we tried XSPF...
The reason of this being actually hard to do is that Liferea only depends on GTK+. This allows using Liferea with KDE, XFCE, Windows and other non-GNOME setups.
With GStreamer and Python via GIR it is as simple as this to get a working media player without any worries on compile time dependencies or codecs support. As a proof-of-concept I implemented a simple three button plugin for Liferea that allows playing music enclosures:
While this is experimental (git master, soon to be 1.9.4) I intend to enhance it to provide simple player control and support videos. When testing this interface several usability questions like "Can I switch to the next item with the song still playing?" already came up. So there is much to do, but this could be one of the next great things in Liferea.
I'm wondering how many of our user will use such a player?
And if you are good at Python and GIR have a look at the plugin code and help building this!