What software do most of you use for book data collection?
I will be using a Mac but cross platform would be even better.
There are two systems I know of that are web-based (therefore, cross-platform) and are popular in church libraries: Atriuum and CONCEPT III. (See their ads on this page's right column.)
Both systems work on Macs, PCs, Chromebooks, iPads, Android, and smartphones of every type. Atriuum is more widely used and is quite flexible. CONCEPT III is a bit more basic, intuitive to use and less expensive. Either will serve your library well.
To be perfectly honest, my church library uses CONCEPT III, and we love it. I do work for Library Concepts. I might have a bias:-)