http://www.apple.com/itunes/download/
There is not much information regarding new features:
iTunes 4.8 includes new Music Store features and support for transferring contacts and calendars from your computer to your iPod.(requires Mac OS X version 10.4).This revision is not available via the software update.
This update is 11MB large.
[update] there is something new :)
Translation: Play video clips: in the main window.
Apple is preparing something related to music and video!!
