The Top Level Categories plugin allows you to remove the prefix before the URL to your category page. For example, instead of http://fortes.com/category/work, I use http://fortes.com/work for the address my “work” category. WordPress doesn’t allow you to have a blank prefix for categories (they insert category/ before the name), this plugin works around that restriction.
%postname or %category%/%postname% — there is currently no workaround