Machinimatrix.org is releasing a new tool for use by Second Life™ creators. This one is called Sparkles Tool Box. The promotional video comes as a tutorial for merging UVMaps and shows people how to perform the task manually. Then goes on to show how much time can be saved by using the new tool.
If you already have AvaStar, you may not need the new tool, depending on your workflow. I have Blender 2.71 and avastar-1.1-beta-4_blender-2-70 installed. When I copy the AvaStar model’s lower, upper, and head and combine them I get the UVMap result that Sparkles provides as shown in the video.
But, if you are working with anything other than the AvaStar model, Sparkles is going to be a time saver.