I have vbscript on this blog that will give you the ability to add a computer to a collection but it command line based. I have created a HTA file that has 2 parts.
1. Allows the user to right click on a collection and add multiple computers
2. Allow the user to right click on a computer in a collection or query and add it to multiple collections
The output list is limited to 50 currently but you can change it per your enviroment. Also I am pulling System Resource from "All computers" collection. I am sure this could be modified to add groups and OUs and such.
Here is the link to look at the code and download the program
http://www.sccm-tools.com/tools/rightclick/rightclick-Collectionaddcomputers.html
I have some ideas to improve it so I might be posting those changes here.
