Help finding a program for photo organization

Hey,

I was just wondering if anybody knows a good program to organize photos in a portable hard-drive.

I need to be able to search within the hard-drive from multiple computers (my airbook, my macbook pro and my macpro).

The objective is to create a digital archive within my hard-drive that makes searching easy, so the program needs to act as a sort of search engine that can categorize as well.

I have tried Adobe Lightroom, and iPhoto is out of the question.

Does anyone have any suggestions?

Picasa can be setup to index any folder or drive and checks for changes each time it connects. Just looks at the folder/file structure.

can you create tags for photos to make searching easier?

never mind, just tried it out. it seems okay. thanks mrplow.

has anyone tried out Shoebox, if so, does it work for portable hard-drives?