I've long been a fan of 1Password from Agile Web Solutions. In my opinion it is by far the best place to store your logins, passwords, bank and credit card details and other confidential information. Apart from being a rock-solid vault for all your secret stuff, 1Password offers a unique benefit – automatic login to your web sites. This means you can use really secure gobbledegook passwords for all your sites and ever need to remember them. True to it's name, you just need the one master password (which is never used on web sites, of course) to access all the rest.
For the past couple of years it has been possible to store the 1Password datafile on Dropbox with the advantage that all your Macs could access the same information and be completely up to date with any changes. Up to now, though, the excellent iPhone and iPad applications have required manual wifi sync and it was a task that had to be remembered regularly. I've had a long-standing repeat task in OmniFocus to make sure all my versions of 1Password are up to date.
This all changes today because 1Password has joined many other similar multi-platform applications in permitting cloud sync – in this case via the reliable and wonderful Dropbox. Now, all your instances of 1Password (even on a PC) will be permanently in sync. A change of password or login details on the iPhone or iPad will be back on your Mac by the time you get home. Wonderful stuff.
More and more we now rely on cloud syncing for all our critical data. Mobile Me (or Mac.com as it was originally) led the way with automatic syncing of Address, Calendar, Safari bookmarks and, even, Mac dock contents and widgets. Now we don't even think about it – we just expect everything to be in sync. Thankfully we are now one step further to automation in data.