Angsumans plugin redirects posts and pages 301
It worked well for me.
It did not redirect /categories/ matbe because of me or the plugin?
Also I could not use .htaccess to do this because I did not have access.
So I ended up using the plugin for a month or so (Google redirected everyting in a matter of days) and then I used a php redirect like for the rest of the site.
// Permanent redirection
header("HTTP/1.1 301 Moved Permanently");
Also see this thread for the Otto42 solution using htaccess. http://wordpress.org/support/topic/84399?replies=5
Maybe there is a better way but that worked for me.