Before 2 weeks I added Md2 animation support to my engine. It was an easy task. MD2 has some predefined set of animations. MD2 is used by games like QuakeII,Sin, Solider Of Fortune .
See the MD2 animations running with my engine(Video lacks clarity because my screen capture software not allows to record at high frame rate with good quality)
While coding MD2 loader i found that the skin path in the MD2 file is relative and sometimes entirely in some other directory. So we cannot rely on this path. In MD2 file they are trying to minimize the model data by using different techniques like having predefined normal vector set. The creators also store texture coordinates as short rather than float.you need to divide by the size of texture to get the real texture uv coordinates.
One other problem is with inconsistent naming convention of frames. say we have 120 frames , and in one Md2 file 10-20 frames contains animation for running data with name "Run001", but in some other file they use "Run__1".. it would be better if the creators have made a standard for frame names.
Finally you can use blender modeler software to create MD2 animations.(i heard it is buggy :) , Thats ok Bugs are everywhere),