Best bone model format

I am programming a game of my own, and I am already 6 months in. I am using OpenGL and SDL to make it, and it is a third-person perspective game. I was wondering what model format would be best to use for my game. I previously used keyframe models, but grew tired with their lack of physics interaction. So I decided to scrap my keyframe model reader, and begin using bone models. I made my own format, but I am unsatisfied with it and wish to use another format. My OS is Linux, Debian distro. Makes no difference, as I intend this game to be cross-platform. I am currently experimenting with Blender, and I hope to use a format that Blender supports. I don't mind coding a reader myself, just a little push and some file specs to get me going. Preferably not .X or a file that has a scene or anything involved; just the model that contains bones, mesh, and whatnot in one file. I will not use any other libraries other than libSDL and libGL, so do not request I use a library to do this for me.