1Password is an incredibly valuable tool for me that I use all the time. Before I started using it, I had moderately weak passwords that were roughly the same on every website for which I had an account. But now I can have randomly generated passwords unique to each website and not have to worry about knowing them--I just need to know one password (a randomly generated, strong one) and that allows me to securely log in to any site.

And the Dropbox syncing is a killer feature--I have the iPhone app as well as the desktop version, so I can view the passwords anywhere if I need to log in on a computer at school (for example).

And, of course, supporting and augmenting that is Dropbox: it lets me easily sync not only my passwords but also my files--I've stopped carrying around a flash drive now--if I'm working on a file at school, I can just upload it to my Dropbox (in the correct folder) and then it's there when I get home, without me having to think about it at all. It's very convenient and I've become somewhat dependent on it.