Blender3D THE open source 3D modelling/animation package with LOTS of features. Saves .x files directly. some featurehighlights: UV mapping/mesh unwrapping, subdivision modelling, game engine (can create standalones!).the gui is a bit special and takes a while to learn but it seems to be quite productive.
Wings 3D open source 3D subdivision modeller. small, fast, easy to use and looks clear.
AccuTrans 3D 3D-file format converter. full working version downloadable, licence 20USD. can write .x (Ascii or binary) but not read. has a good function to create 3 different styles of texture coordinates for the models.