Mudbox 2011 has a new Posing toolset and Wes McDermott shows of some of the capabilities in this short post and video. With Mudbox 2011 you have options to create joints as well as paint weights. You can also import full skeleton rigs via FBX into Mudbox 2011, so you can rig and weight a model in maya and bring that into mudbox with all the joints and painted weights.
