During development, internal storage size is severely needed. Cache cleaner is ok, however, apps have another component called data which can be cleared. Is there an app out there that organizes by an app's data size ? I'm not interested in app size, I'm interested in app's data size.
I know this answer's a bit late, but you haven't received a good one yet!
In Titanium Backup, you can do Menu -> More -> Overview of app storage use, then order by data size. Not only will you have your apps sorted by data size, TI shows you the size with graphical bars, so you can compare apps at a glance and see what's huge vs. tiny. See the last screenshot on the market (the free version) for an example.
Another option: App 2 SD by Sam Lu. Not as pretty, and the apps are split over 3 screens, but it is possible by doing Menu -> Sort by -> Data size.
Finally, if you have a rooted phone and an ext partition, you can move some or all of your data to the ext partition and gain tons of space!
1Tap Cleaner is capable of that, I use it all the time to clear data-hogging apps.
Once in the app choose Cache Cleaner then bring up the Settings > Sort by Size > Data size.
Check out DiskUsage. It'll let you see what is consuming the most space on either internal or SD card.