There are now 177 million domain names across all top-level domains, which is an increase by 16% (24 million domain names) compared to a year ago.
These numbers are from the latest Domain Name Industry Brief, a quarterly report from Verisign about the growth of the domain name industry. Verisign has been doing this report a few years now, so we went back and looked at the data for 2006 and 2007 as well so we could show a wider time frame than just 2008 (to see trends, etc).