Apache lightweight web servers alternatives

Apache is a very complete and modular web server, but when it comes to performance it might be a little behind, especially to support multiple concurrent connections. This collaborative comparison try to list the alternative web servers, you might consider.

Performance

Any of these web servers will perform better in terms of CPU or memory usage in a highly concurrent scenario.
Some biased resources: cherokee-project.com/...

Popularity

According to netcraft web server survey, Nginx is the most used from these alternatives, then comes Lighttpd. The other alternatives present here are not listed. netcraft.com/...

Features

All alternatives have almost the same common features, Fast CGI (to support PHP for example), HTTPS (SSL support). The notable differences are on the administration parts, some have an integrated interface to manage easily the web server; other will only rely on command lines and configuration files.

Switching

If you already have an existing Apache installation, before switching to another web server make sure all the features or modules, you are using, can be replaced on the new web server. The next step would be to find a guide to convert your Apache configuration files. The conversion and testing part, will probably be the most consuming task to switch from Apache to another web server.

Keeping Apache in the background

If you really need all the Apache features, you can still run Apache behind Nginx or Lighttpd as a reverse proxy.

Feel free to add any relevant criteria or alternatives to complete the comparison table.