What can I do to manage my phone's internal storage? If you're not used to seeing the 'low on internal storage' notification, what is it that you're doing to keep your phone's internal memory from filling up so quickly? 

The 'SD Card and Phone Storage' menu in the settings doesn't really tell me much other than how much is free. And, I don't really have that many applications installed. The top 5 storage hogging apps on my phone are Gmail (18.6 MB), Twitter (17.5 MB), Facebook (12.55 MB), Maps (9.63 MB), and Swype (6.06 MB).

So, are there apps out there (besides your normal file manager ones, like Astro) that will help monitor internal phone storage? Is there something I should be doing to keep my phone storage use to a minimum?
I'm using an app called DiskUsage which helps visualize what's using both my internal storage as well as the SD card.