Quite a few apps for me (Facebook, twitter, Dropbox) seem to get larger and larger (eg if i preview a file on dropbox), i cant see an option to 'delete the cache'. Sometimes i see twitter 'cleansing' which i presume means getting rid of old stuff A pain but i often delete those 3 apps and re-install and then get back the 150 meg or so But yeah the initial post doesnt help us much, is he moaning about the music size or something else ? I presume you've got an 8 gig device ? I've got a 64 gig device but obviously i cant use all the 64 gig I would back everything up and reformat it to see if that makes a difference
You need to sync with iTunes and then reboot your iPhone. This will delete cache and give you more space back.