There are many database software packages for the Axim, but I've found Sprint DB Pro to be way on top. With any of them, you can sync Access databases, but Sprint DB Pro is the most sophisticated and user-friendly out there. Try it out at Handango.
As far as the ruggedized case goes, I've been looking for one too. Here is one that looks attractive:
http://www.mts.net/geo/armor.htm