I am pretty much a hands-on, old school, manual arts type person.
this said, I was recently shown this amazing metalsmithing tool - the imakejewelry app for the iphone (or ipod touch), by incredible jewelery artist Victoria Lansford.
I would usually scoff at some techie thing like this... but this is AN AMAZING BENCH TOOL. every imaginable gauge, weight & length conversion, ring sizing by gauge, and all sorts of info on stones... IN YOUR POCKET!
all that and it's under four dollars. worth it's weight in silver.