Open Web Server
In a recent project i´ve got the impression, that Apache is a good webserver, but as soon as you loose the frequently used trails, you are on your own and the quality of the code seems to deteriorate. But there alternatives like lighttpd and nginx, but those are lightweight webservers developed for some special use cases with their own share of issues (the fcgi integration wasn´t stable enough for me to keep c0t0d0s0.org on lighty. The Apache one is more stable, but i found out at other sitations that the apache implementation isn´t 100% stable as well but i found this problem at 1000 requests/second despite all tuning).
Many people doesn´t now, that there is another alternative: The Sun Java System Web Server (SWSJS … i hate this marketing name). Featurewise it plays at least in the same ballpark as Apache, many large sites use it for sites with extreme load.
Apache may run on more websites but SWSJS has a large share at the high profile/high load sites) You can download and use it for free at the Sun Website. At wikis.sun.com you will find a good source of information and documentation about this webserver. When you like it and you want to use it in production you can buy a license and support for it (but you don´t have to). In 2007 there was a good review of the SJSWS in Serverwatch:
In summary, Sun Web Server is generally two times as fast as Apache. Both tests fetched a 44-byte document and ran on a slow Sun Netra X1 400MHz server. We had a SunFire X4600 available to test with, but it seemed more impressive to test this server on modest hardware. The Sun Web Server is fast, flexible, scalable, and a downright joy to run. Other Web servers may still have some benefits, mainly because of administrator familiarity, but if performance and ease of management are paramount, Web Server is the way to go.
And for all this PHP lovers: You can compile PHP with NSAPI support or use the precompiled PHP add-on.
And since a few days there is another reason to use SJSWS: The core of it was released as open source as the Open Webserver under a BSD license.
Open Web Server is derived from the core of Sun Java System Web Server 7.0. Open Web Server is a highly scalable multi-threaded HTTP engine capable of handling hundreds of thousands of simultaneous HTTP connections. Open Web Server includes common interfaces for adding dynamic content including SHTML, CGI, FastCGI, and its own native interface, NSAPI. With connector plugins Open Web Server can easily be used with popular Java application servers such as GlassFish, Geronimo, Tomcat, JBoss, and more. Open Web Server features support for access control, LDAP credential store, SSL, and Elyptic Curve Cryptography (ECC).
You will find the projects website at wikis.sun.com, too.