One of the many things I use my iPod Touch for is to store databases of information I want access to on the go such as books I have, books I'm on the lookout for, car maintenance histories, etc. Bento fits the bill nicely for my purposes and there's a Mac version which allows you to synchronize your databases between a Mac desktop or laptop and your mobile device.
It's a full featured database with optional field types such as check boxes, choice boxes, text, dates, numbers, and other options. It makes data entry very easy which is important on a mobile device. One of the things I like about Bento is it's one of the few inexpensive lightweight single user databases available these days. In the old days there were lots of database choices for users on a budget.
I read today that there's a version of Filemaker Go for the iPhone/iPod Touch/iPad. It synchronizes with Filemaker Pro which is available for Mac or Windows. Filemaker Pro finally makes it easy to sync between a mobile device and Windows. The upside is it's a more powerful database than Bento is if your database requirements are a bit more advanced than Bento's feature set. The downside is it's more expensive than Bento.
So you've got another database option if you're a iPhone/iPod Touch/iPad user. It's good to have choices, eh?