I'm a great fan of 1Password from Agile Web Solutions. I've been using it for a several years on the Mac to store passwords, software serial numbers, and credit card details, in a very secure form. There's a sale on for the Mac version, and important info for iPhone, iPod Touch and iPad users.
If you're an iPad user and already have 1Password Pro, you need not purchase the iPad version. Just update your iPhone app, and all of the features of the new iPad version are included in the new version of 1Password Pro. Users of the standard version of 1Password by the iPad version for $6.99. Another option is to simply buy the Pro version, which covers iPhones and iPads completely for $14.99, and keep it all in one app for your iPhone and iPad. Of course, the iPhone 1Password standard edition runs fine on the iPad, like nearly all other iPhone apps, so if you don't need extra features in the iPad interface, you don't have to upgrade at all.
If you're not a user of 1Password on the Mac, this is a good time to consider trying it. Agile Web Solutions is having a sale in honor of the iPad's release, 20% off for a limited time.
With the news bits out of the way, what is 1Password?
Here's a summary from Agile's web site:
- Go & Fill: 1 Click, That's It: Selecting one of your saved logins from 1Password's Go & Fill menu takes you to the site, securely fills your username and password, and logs you in, all with a single click or a few keystrokes.
- Online Shopping Made Even Easier: Once you've created your identities, select one in your web browser to quickly fill out a contact form. Store multiple credit cards to simplify and speed up your online shopping, filling checkout forms with ease.
- Always By Your Side: Now you can take your information with you so that it's always on hand. Mobile versions of 1Password are available for iPhone OS and Palm OS and more data portability options are coming.

I really want an iPad!! Looks so cool. :)