Two small scripts I wrote detail disk usage (root and /home) for each package installed by you (rather than the base OS)

http://chris.intrepid.cx/N900/debug.sh
http://chris.intrepid.cx/N900/diskspace.sh

Open those links in your browser
Save them in the Document folder
Open an x term

type:

sh MyDocs/.documents/debug.sh

then wait about 30 mins.. this script does a lot of extra stuff you don't need

When it has finished run

sh MyDocs/.documents/diskspace.sh MyDocs/debug.tgz

You can see which packages (at the top of the list) are eating most root space..