Without having to add any plugins, just by adding some lines of code to your themes functions file you can make pages or posts visible depending on the users. Perfect for company blogs, intranets and wiki style WordPress sites.
To learn more visit this link on about.com.
Jim Callender is a Freelance Wordpress Developer. Living & working in Brighton. He started working with Wordpress in 2003. Since then has been responsible for delivering high profile sites for a number of large UK design & marketing agencies. His other site is www.jayonline.co.uk