WebTitan is a great SAAS proxy server with excellent features. You can allow and block website base on their types. You can whitelist some domains so they never get blocked if they are under blocked category and you can blacklist some domains so they are always blocked if not included in blocked category. With WebTitan you can also add role based user for management.
I really like creating and installing certificates to by pass or allow traffic for specific period of time. It make management so easy. I also really like the alert functionality that can notify you if someone tries to access restricted websites.