I had much the same issue, couldn't figure out what I'd installed that was using all the space - 'storage usage' pointed me in the right direction for some things. Anyway, the comment (linked below) should start you on the right path, though some of the things the individual linked do not need to be any longer because they already are in PR1.2.

This post a few pages back fixed things

I've saved about 80 megabytes by using symbolic links for a bunch of stuff in /usr/lib /usr/share and a few odds and ends in /var

No performance impact, though I picked things that largely don't matter a great deal to me.