Is there any alternative to OpenDNS?

Google Public DNS   

It depends which features of OpenDNS you use - if you want the extra filtering and other such your options may be more limited. Also, telling us why you are looking for alternatives (nxdomain handling? reliability problems? just curious?) would help in getting good answers.

Google have recent started a public DNS service, as stated by Paul's response, which may suit your needs.

If you run your own servers or virtual servers then you could also run your own private DNS service, but as this question is on SO not SF I'm guessing you are a home user rather than a server/IT admin so that would probably be massively over-kill for you!

Many people have good speeds with Level 3's DNS.

That's 4.2.2.1 to 4.2.2.6, so very easy to remember.

Google have a good new DNS service, at 8.8.8.8 and 8.8.4.4, so ALSO easy to remember.

UltraDNS is very similar to OpenDNS, in that it tries to provide a little more control, but I've never used it, and it doesn't appear to be free.