The biggest file I'd like to get rid of is the locale cache and unused locale data from rootfs. I only use one language so would love to blow away/rebuild this 22.8MB file (safely). I've got about 50MB freee on rootfs, so it's not currently a burning issue, and I haven't seen any process that looks foolproof on the n900 like there was on the n810 (the localepurge script).