You need an smd exporter for blender. For ragdolls you’ll wind up exporting a total of 3 smd files, one for the model itself, one for the skeleton, and one for the collision model. I’m pretty sure it’s the same deal for a static prop. After that, you’ll need to set up a .qc file that tells a program, such as studiocompiler, what to do with the .smd files. You use studiocompiler to compile them in to the various files you’ll need, including the .mdl. As for materials…I haven’t gotten that far in my attempts, so hopefully someone else can tell you what you need to do. If you search around on that site digigamer linked you to, you’ll find lots of helpful info on all this. I’d link you to a tutorial, but the only decent one I know of is for 3ds max, not blender, but I know there are some tutorials floating around. Just do a search for “modeling for source in blender”, I think it’ll lead you to a youtube video tutorial.