What's taking up all of this "Other" space on my iPhone? I have a jailbroken iPhone, and it's low on space. Much of the wasted space seems to have been consumed by the "Other" part of the space display in iTunes.

How can I get a breakdown of how that space is being used? The restore process from my backup may have left some extra crap around, so I'm thinking that maybe some of it's just incidental data that I could clean up if I knew what was there.

On my mac, I'd use DaisyDisk or something like it; does something like that exist for iPhones?
This space is taken by Application Metadata, and is also taken by Jailbreak applications since iTunes doesn't know that these are regular apps. Doing a full restore of your iPhone through iTunes should clear up this space. There aren't any utilities like DaisyDisk for iOS and the closest thing is iFile on Cydia, an application for managing the files on your device.