OpenDNS is the cutting-edge Internet service by a San Francisco-based startup founded by David Ulevitch. Simply put, with OpenDNS you are no longer tied to using your ISP's slow DNS servers. I have been using OpenDNS for almost a month now and I can tell you that there are more than just speed improvements. Before I get into it, let me explain the whole DNS model.
As I mentioned in How To: Start Blogging, whenever you access a website your computer first contacts a domain name server (DNS) to find out what server IP address is paired with that particular domain name. By default without any configuration your computer automatically uses DNS servers provided by your ISP which are commonly overused and slow. As Chris Pirillo pointed out, you can experience anywhere from 50 milliseconds to a second or more when dealing with slow DNS's before your computer can interact with the actual website.
Enter OpenDNS. By configuring your computer to use the domain name servers at OpenDNS you can benefit from more reliable and faster DNS servers and queries. But it doesn't stop there - OpenDNS provides protection against known phishing sites and allows for a user-friendly Internet experience with on-the-fly TLD (.com, .net, etc) spelling corrections. As OpenDNS begins adding features you have the ability to control them via a preferences page on the site. Their service truly gives you some control over the Internet.
To the end user, the OpenDNS service is truly transparent. You won't really notice that you're using it with the exception of the speed and security improvements. It does nothing to hinder your browsing habits. There are however the few times when it doesn't know of the website you are trying to access and treats your address bar entry as an OpenDNS search engine query. For the little time that OpenDNS has been public and active, they seem to be handling the load quite well with over 60 million DNS queries daily.
Okay so now that I've got your attention you're probably wondering how you too can start browsing with OpenDNS. It's rather simple, all you need to do is tell your computer (or router if you're on a network) to use the OpenDNS servers whose IPs can be found on this start page. Fortunately, they offer comprehensive guides to setting it all up. However there are some situations where OpenDNS won't work. When I was in California, OpenDNS refused to work on the hotel internet (behind a network). The only thing that really matters to me at least is that I'll be able to benefit from OpenDNS at home and in this case it works perfectly.
In OS X, configuring OpenDNS is as simple as dropping in these two IP's in sys prefs » network » configure ethernet/airport » TCP/IP
OpenDNS is on my "startups to watch" list - I can see great things coming from them in the near future. Imagine having a control panel for your entire Internet experience. OpenDNS is the company that can make it happen.