I quite new to the raspberry pi because I only just received one for Christmas. However, I'm not new to linux at all because I'm a actively part of the lowendtalk (google it) community which attempt to do run extremely optimized server setups using very low end linux virtual private servers.
I decided to try and configure the raspberry pi as a fully functional web server exactly how I would with one of my low end virtual private servers. I was interested to see how the raspberry pi would perform as a web server because it has a 512mb ram (I'm used to working with 32-128mb ram).
For this webserver setup I have overclocked the CPU to 900mHz and set the GPU ram to 32mb (because I'm not running the GUI). I am running Nginx, PHP5-FPM, MYSQL and Proftpd as part of this setup.
Here are the results while the server is idle -

I quickly found out that CPU cycles was going to be the bottleneck for virtually any web application so I decided to enable php-apc to cache some php and hopefully to save some cycles.First of all I tried wordpress. The results weren't too great even with heavy caching because the raspberry pi simply hasn't got the processing power to process all the PHP and MYSQL quickly. As a result, I had to ditch wordpress and explore other options because I want a responsive blog hosted on my pi.
I decided to use Blite (http://blite.ca) as its a great lightweight blogging application that doesn't even need a mysql database. So if you want a minimal blog webserver setup then this is for you!
You can test the speed of my blog here - http://rstreefland.com
Thanks for reading, if you have any questions fire away! (I may post a tutorial if there is any interest)