I use the Covertec leather case:
http://shop.treonauts.com/content/ac...s/4-25--19.htm
Nothing too fancy but
--it's slim
--has a solid belt clip (no plastic swivel) that can still move
--easy to open/close
--looks sharp
Here's a good review/selection of the "best" from Andrew at Treonauts:
http://blog.treonauts.com/2006/09/the_case_for_a_.html