I use a Seidio hard plastic screen protector and the RIM leather pouch. I keep mine in my pocket, not on a belt. The good thing about the Seidio is that you just stick it on there (no water, etc), and it won't scratch and no edges will peel away. I've have mine over a year and looks like new. It does cost more than the ones that you cut and paste on. The pouch protects all the keys, the trackball (even the screen). Has a magnet to shut off the display when you put it away.
BB 8900 Tmobile, Moto Droid Verizon