From: https://community.spiceworks.com/topic/336235-best-web-filtering-solution

My three favorites listed in order of preference:

OpenDNS - http://www.OpenDNS.com
Barracuda Web Filter - http://www.barracuda.com
Untangle - http://www.untangle.com

From: https://community.spiceworks.com/topic/832661-need-something-for-content-filtering

Depending on needs, you can also do DNS level filtering - it's not perfect but it does in a pinch, 
and it's easy to set up.  Dyn has a product called Internet Guide that's $20 a year (even for businesses) 
that does 98% of what OpenDNS did before they went Umbrella.  

From: https://community.spiceworks.com/topic/1655287-web-content-filtering

From: https://community.spiceworks.com/topic/884423-open-dns-recommended-alternative

From: http://www.dnsredirector.com/compare/

From: http://dyn.com/products/