My ISP's DNS was in the toilet for awhile in 2006. After surveying the options, I switched to openDNS, which at the time was new, and I have used it ever since. (At the time, the creator must have been googling for references to his service. I was participating in a discussion of it on some bulletin board and the guy would chime right in, defending the service when skeptics posted, and helping people who were having problems understanding it or using it. I suspect he's too busy for that now.)

As ScottC pointed out, it takes you to a page of suggestions if you try to go to a non-existent site. It also has some anti-phishing features. The wikipedia article on openDNS has a brief overview with pros and cons.

One small annoyance: Rarely, no more than once every couple of months or so, it tells me that a site is not loading even when I know darn well it should. When that happens, I use the openDNS "CacheCheck" page, which will sometimes make the site accesible. If all else fails, I launch AOL (now free, BTW, for people with their own broadband access) which has its own DNS.

see "How we're faster: Global footprint" at http://www.opendns.com/how/faster/global-footprint/