Have a crap cell-phone and are looking to increase the signal-strength? This video shows you how to create your own antennae. I am unsure if this will help those with cell phones that already have antennas, but I am assuming no.
http://www.2dayblog.com/blog/2008/01/20/2days-how-to-boost-your-cellular-signal/?lang=en
http://www.2dayblog.com/blog/2008/01/20/2days-how-to-boost-your-cellular-signal/?lang=en