I was reading my Windows IT Pro Magazine, and saw an article where they had an HTA file to map the next available drive. This seems to be a lot of work for something that can be done from the command line:
Net use * \\servername\sharename /user:mydomain\myname
For short term use, I prefer to use the pushd and popd commands. Either way, spending the time to write a vbscript (or HTA) to map a drive is a waste of time.