I've mentioned this in the past, but we continue to get questions about it so I thought it would be wise to re-iterate it. Many Web marketers will purchase extra long domain names so that they can include more keywords within it. Some engines are believed to boost your ranking if your keyword also appears in your domain name. The "official" domain name size limit is 67 characters if you count the ".com" or other extension at the end. However, you should NOT register any domains exceeding 59 characters. There are reasons for this:
1) Netscape browsers are known to throw fits over URLs that exceed 59 characters.
2) AltaVista has been reported to reject URLs that exceed that same length as well. However, domains under 60 characters seem to be fine.
3) GoDaddy enforces a 63 character limit.
On the same topic, I'd be wary about using any domain name that is ridiculously long. Including three or four keywords should be fine. However, the search engines could, if they saw too much abuse in this area, discriminate against URLs that are excessively long. I've not seen hard evidence that this has occurred. I'd be interested in hearing feedback from users on whether they have documented anything good or bad regarding extra long domain names.
More importantly, you risk alienating users. Face it, typing in long domain names is a pain. The average length of a domain name is 11 characters.
If you're looking to register a new domain for whatever reason, you can do so at many locations on the Web.
Note: The information presented here adapted, under license agreement, from FirstPlace Software