Blender is free and has a super easy method to assign the mesh to bones: build your mesh and your armature much the same as in any 3d suite then parent the mesh to the armature and use the option "create vertex groups by bone heat"
It'll auto-assign and weight vertices to bones based on proximity, you can then go and clean up the vertex groups manually by weight painting, or assigning values to selected vertices.
That being said, a simple skeletal armature which can deform a mesh is not a true "rig". It can get the job done for posing and simple animations, but if you are wanting good, detailed animation do some searching for examples of good animation rigs with IK.