Kritton is a very compact and fairly efficient webserver under development, supporting most of the rudimentary features other HTTP daemons support, like CGI scripts and Virtual Hosts, while at the same time being free! Although Kritton is hardly in Beta stage, it is very promising, for features are being added constatly.
Without of course being very popular, Kritton is very good in terms of security because it has the ability to perform a chroot()and enjoys security-minded code. In terms of performance, Kritton is considered to be a fairly fast webserver for HTML files ( blazing fast if the traditional fork()ing is taken into account) and close to excellent in terms of CGI performance.
The project has many esoteric functions that other webservers don't, for instance, a stat() cache. This helps increase efficiency. Kritton, having just entered the Beta stage and getting more ready for normal use,is also quite stable. Of course, its development stage is mere Beta, it does seem to avoid segmentation faults very well, and even if one occurs, it is not fatal due to the parent pool. Even in the case of being fatal, Kritton can be ran within a wrapper script ( a sample one is provided), so in the case of an error, it can be restarted without delay.