apache

Apache module mod_logio provides the logging of input and output number of bytes received/sent per request. The numbers reflect the actual bytes as received on the network, which then takes into account the headers and bodies of requests and responses. The counting is done before SSL/TLS on input and after SSL/TLS on output, so the numbers will correctly reflect any changes made by encryption.

Apache's mod_rewrite provides ways to map values to attributes using the directive RewriteMap. RewriteMap can use flat mappings files, hashed mapping files, internal functions and external rewriting programs. One not well known feature of mod_rewrite is to extend this functionality with internal functions, defined in a separate Apache module. This allows to do complex and time consuming mappings, since the mapping request does not have to be passed through a single communication pipe, as in the case of an external rewrite program.

nginx [engine x] is a HTTP server and mail proxy server written by Igor Sysoev.

nginx has been running for more than four years on many heavily loaded Russian sites including Rambler (RamblerMedia.com).
In March 2007 about 20% of all Russian virtual hosts were served or proxied by nginx.
According to Google Online Security Blog year ago nginx served or proxied about 4% of all Internet virtual hosts, although Netcraft showed much less percent.
According to Netcraft in March 2008 nginx served or proxied 1 million virtual hosts. The growing in picture and colour!
According to Netcraft in December 2008 nginx served or proxied 3.5 millions virtual hosts. And now it is on 3rd place and ahead of lighttpd.
According to Netcraft in March 2009 nginx served or proxied 3.06% busiest sites.