Android only: If your Android phone gives you grief about running out of space, or you're just curious as to what's taking up room, DiskUsage has the scoop. The app provides a basic visualisation of your phone's internal and SD storage spaces.
It's nothing quite so pretty as, say, Disk Space Fan for Windows, but DiskUsage does offer a keen map of where all your space goes. For those running low on internal space, it's mostly handy for seeing which apps take up the most space (and which can then, hopefully, be moved to your SD card). For those with microSD cards pushed to their limits, you can determine whether the focus should be on music, pictures, downloads or app storage when you get to cleaning up.
DiskUsage is a free download for Android phones only. You can grab it from the Market using the QR code at left or search for "DiskUsage".
diskusage [Google Code]