Update: Moxier Wallet officially shut down June 2013.
To be on the web today means to acquire dozens of usernames and passwords for accessing data. And many people get lazy and use the same password for every site, which can put some of your content at risk. If someone gets a hold of your username and password for one site, suddenly access to your online life can be vulnerable.
A number of applications have sought to provide a solution. The latest is Moxier Wallet. Its approach is one of the most comprehensive I have seen, with access and syncing between a PC, Mac (still to come), and iPhone.
The iPhone version of Moxier Wallet works best if you also have the software on your computer, as there is quite a bit of interaction with text that may take place. Moxier Wallet doesn't just store your passwords, if you want some blockbuster, hacker-proof combinations, like xK389.&mow*2d it will generate those for you. There is a sliding scale for how tough you want to make it, going up to 20 characters of mixed randomness.
Tap once on the password text, and it automatically copies it for pasting into Safari or another app. Editing and creating new profiles is pretty easy. The only section that was a bit jumbled was the categorization of the password accounts. I found it easiest to simply display all accounts and then use the search option (the same functionality is also available in the Windows and forthcoming Mac version).
As for security, Moxier Wallet says it uses top-of-the-line, military grade encryption. For extra measures there is a premium level of service available for $19.99 per year. That gets you online backup to all the data you store.
Apps and developers tend to come and go in the App Store world, but hopefully since Moxier Wallet is made by Emtrace Technologies (a company that has been in business since 2000) your data will stay safe and secure for a long time to come.