I can't help saying the openDesktop.org is a little unstructured - and it's actually difficult to find stuff. Just try searching for Gimp and see the around 70 hits you get - very confusing.
I prefer using Open Source Alternative http://www.osalt.com/ - they provide good descriptions, focuses on high-quality (useful) open source software. It's not cluttered with small sub-modules - just a great open source applications.
And for beginners in the open source world - just search for your favorite proprietary software - and up pops all of it's open source alternatives.