Greg Hamer gave a fantastic presentation today as part of the Adobe Developer Week seminars on Local Data Storage Options with AIR. I think it's safe to say that Greg overprepared his material as it was run and gun from the start. If you like rapid fire learning, this is your guy.
Greg covered all the options available in AIR, demonstrated side by side read/write benchmarks for each, and discussed the pros/cons of each method so you can choose the most appropriate for your needs.
The four options available are:
1) Local Shared Objects
2) Encrypted Local Store
3) File System
4) Embedded SQL Database
Greg posted his slide deck, a link to his recorded session, and sample code on his site. It's well worth a look.