It depends on how much knowledge and experience you have. The server-type Linuxes are CentOS, Debian Stable, and Slackware. If you look at the annual survey of websites, CentOS and Debian are the most common. In my opinion, CentOS is the easiest to install and use. If you get the 2 DVD version, the installer gives you options for different types of installation, including basic server, database server, and web server, and then gives you exactly the stuff you need. The documentation is probably the best, too: if you look at their website, they link you to the Red Hat documentation, which is excellent.
PS.. I've nothing against Slackware -- on the contrary, I prefer it to Debian -- but it can be a lot of work. If it scores highly in LQ Members Choice awards, that's because it has no forum of its own, so all the Slackers come here.