I have just changed my router settings to use OpenDNS's servers instead of the DNS servers provided by my ISP. The change was easy enough; just a matter of typing two new address into the routers settings page.
The effect of the change is that whenever I request a web page in my browser the address of the web server that holds the page is found from the OpenDNS servers instead of those my ISP. There was nothing to install, and no need to open an account. Though you need to open an account if you want to use some of OpenDNSs other services, such as adult content blocking. I am testing OpenDNS because I am interested in their anti-phishing service.
I had been wondering how often I had clicked on a link to a phishing site. I have Firefox's ant-phishing feature enabled and never had a warning message. Perhaps that was because my natural cunning meant I never visited phishing sites. Or, perhaps it meant that Firefox's filters were not very good. OpenDNS keeps their own blacklist of phishing sites and if you try and go to one of those you get a message saying access is blocked. I will try their service for a while and see if I get any warning messages.
Anti-phishing is not the only service offered by OpenDNS, but it is the only one I would be interested in.
"OpenDNS is not, as its name might seem to imply, open source software.
OpenDNS earns a portion of its revenue by sending the user to an OpenDNS search page when a domain name that he has entered is not valid. Advertisements are displayed on this search page to help fund the operations of OpenDNS. While this behavior is similar to VeriSign's previous Site Finder, OpenDNS states that it is not the same, as OpenDNS is purely an opt-in service (compared to Site Finder's effect on the entire Internet, as VeriSign is an authoritative registry operator) and that the advertising revenue pays for the customized DNS service." Wikipedia
I wonder if they also make money by selling customers usage data. They know which web pages you are visiting and that information is valuable to advertisers. They do not say they are doing that, and I have no evidence that they are. It is known that some ISPs are selling their customers usage data.