OpenDNS – I use it and like it and yield it like a Zen master: OpenDNS
Regardless if any blocking is used, the tool still provides an auditing/oversight function. OpenDNS is a high availability DNS service; it has a very proven track record of dependable service. If there were a cost it would be sellable; however, it’s ‘free as in beer’ so that is an even easier sell. If for nothing else it could be used as an introductory mechanism to helping your client discover the value of such web oversight of his office staff. Some would rather not bother; some will require access to this information on a as-needed basis, some are overreaching power mongers. It’s not a one size fits all thing.
As for if you trust them in their expressed intention of being a good neighbor in the ‘net’ as to their reason for providing this FREE service, that’s for you to sort out. As a skeptic looking for my clients best interests, I’ve not been given any telltale signs of any bait-n-switchery or other less than forthright underpinnings. It seems legit.
One downside I’ve discovered with OpenDNS is with optionally your logo integrated; when done your logo is displayed on an informational html page whenever something doesn’t resolve or is blocked. Although at first I thought this good in that I’d have a track back mechanism for people who were false-positive blocked that would enable finer adjustments, white listing, …etc. However, instead it put me in the position of a web ‘door-man aka bouncer’ of sorts. I really don’t advocate putting yourself in that front and center thug/gate-keeper position unless you have a service agreement in place as well as some pre-existing expectations, instructions, and explanations as to the who?, what?, and why? of web filtering in writing and distributed to all under your wise and almighty judicious power. 🙂