"Wordpress
Why it is a success: Since its launch in 2004 as a fork of the b2
blog software, Wordpress has become a dominant and hugely popular
blog platform. In a survey we made back in January, 27% of the top
100 blogs ran on Wordpress. If you also counted Wordpress.com,
Automattic's hosted Wordpress service, that number rose to 32%,
more than any other blog software. Since then there have also been
some changes, such as the nine Wired blogs in the top 100 switching
from Typepad to Wordpress.com, so that percentage is likely
significantly higher now (all else unchanged, it would be 41%).
BIND
Why it is a success: BIND (The Berkeley Internet Name Domain
Server) is the most widely used DNS server software on the
Internet. The first version of BIND goes all the way back to the
early 1980s and has been the main DNS server on UNIX systems ever
since. It can justly be called the world's de facto standard DNS
server."