Here are a few Great open source apps i am using and most which i would definitely recommend to anybody, even if your not particularly skillful with software, these applications have such an easy user interface utilizing should be a breeze. I put them in a list so it is easily browsable .
The premier free, open-source browser. Tabs, pop-up blocking, themes, and extensions. Considered by many to be the world’s best browser.
Video Player / Video Podcasting
Beautiful interface. Plays any video type (much more than windows media player). Subscribe to video RSS, download, and watch all in one. Torrent support. Search and download from YouTube and others.
IM – Instant Messaging
Connect to multiple IM accounts simultaneously in a single app, including: AOL IM, MSN, and Jabber.
Powerful spam filtering, solid interface, and all the features you need.
Simple, lightweight aggregator.
Solid cross-platform RSS client.