TopMod is pretty slick and complete open source modeling application with a unique workflow.Â It isÂ officially available for Windows andÂ OSX.Â ButÂ a Linux version is available.Â 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.Â Definitely a good companion applicationÂ with Blender for specific modeling tasks.