Question: I've traditionally deployed my sites under apache, simply by default. I've heard things about NGinX though and I'm wondering under which conditions it would be superior. In addition to apache and Nginx, what the other options are for webservers and what are their benefits?

Answer: 
Apache can be a bit heavy, and can fall over when under heavy load. There are lighter weight servers available, including nginx, lighttpd, and cherokee.

These lightweight options can be set up to serve static files quickly, and delegate dynamic server-side work to Apache.
[Netcraft](http://netcraft.com/) tracks market share of web servers & according to them, IIS stands second after Apache with a 26.03% share (as of July 2010). This is based on a survey of 205+ million sites

[This link](http://blogs.iis.net/bills/archive/2007/05/07/iis-vs-apache.aspx) has reasons why you should check out IIS7 if you use Apache today