Nem's tool Crafty can import "Half-Life 2 .bsp, .mdl, .vmf and .gl formats along with Half-Life .bsp, .mdl, .map and .rmf formats in a variety of render modes."
http://nemesis.thewavelength.net/index.php?p=45and then you can export those as a .obj, which is pretty versatile. I'm not so sure of the extent of the material support, it says it can though.