I use WINGS3D! The learning curve is reasonable, and for a free app, it rocks. Does everything that you essentially need. It's on par with BLENDER and the pay app HEXAGON, but it's much easier to follow - probably even easier than K3D. I own BLENDER, WINGS3D, K3D, Splatch3D, some king of beta nurbs / glunk modeler that came out a long time ago, and several offer off name flash in the pan freebie modelers, and the only one that I really even use is WINGS3D.
Learn it and it becomes intuitive second nature.

http://www.wings3d.com/

Comes in Linux, Win 32, Win 64, and OSX flavors.