I have recently wrap the extraordinary convex decomposition library of John Ratcliff. I did it with the 2007 version. I have added some functions (from John's as well) to find the best fitting capsules, spheres and oriented boxes of convex hulls.
The 2007 version has some bugs that I am currently fixing but it works fine. If you want a more robust version you can get that one of 2004 which is the one that the guys from Bullet have wrapped. I wrapped it as well and it works just perfect. The disadvantage is that it does not include best fitting features and that the splitting plane of concave objects is not always the best. Besides, it is implemented using floats instead of doubles.
John did a great job. At the beginning I tried to implement the convex decomposition myself, but I had some troubles trying to find the best fitting plane. It worked in some cases but in others it failed terrible. So, I decided to wrap John's convex library. It is a bit slower (since it computes the decomposition in a "brute force manner" but it is worthy to wait 30 seconds for decomposing a concave object of 700 triangles into a set of convex hulls.
I will use this together with my GJK implementation :)
Click here for the link of John's convex decomposition library. If you use it, feel free to donate something to John's son association.