I managed to get a in-depth view of what is using storage space, but it's really non-trivial to do.
- Install iOS SMB server (You have to add an additional Repo to Cydia - It's Here)
- Mount iOS device on desktop over SMB
- Purchase iFile, which has a WebDAV server built into it.
- Run WebDAV server on iDevice
- Mount WebDAV server on desktop. I did it on windows using NetDrive. I'm not sure what to use on OS X
Unfortunately, for some bizarre reason, all applications are in folders named using GUIDs, rather than the software name, so you have to actually explore large folders to figure out what app the folder contains. Fortunately, it's generally pretty obvious what the app is, since come of the subfolders seem to have to be the app name.
Alternatively, iFile automatically cross-references the app name with the folder name for you, so you can determine what each folder is using ifile as well.
On the whole, if all you need to do is see what apps are taking up what, it's probably not worth the effort. On the other hand, if you have already jailbroken (Which you should do anyways - it gives access to many great utilities), it's fairly simple to do.
Also, iFile is probably one of the most useful apps for an iOS device. I highly recommend it.