TopMod is pretty slick and complete open source modeling application with a unique workflow. It is officially available for Windows and OSX. But a Linux version is available. Quite a few tutorials are available. I recommend taking a look at the video tutorials.
Quote from the TopMod website:
TopMod3d is a free, open source, portable, platform independent topological mesh modeling system that allows users to create high genus 2-manifold (watertight) meshes.
Visit the TopMod website for more details including where to download. Use the link above to locate how to install a Linux version. Definitely a good companion application with Blender for specific modeling tasks.
