Apache is Apache and it's packaged for virtually every distro out there. It really depends on how deeply you want to dive in right off the bat. An Ubuntu desktop will be simple to install but will be really huge compared to just what you need for Apache. If you want a leaner, more direct install then go for either the Ubuntu alternate install disc and just do a LAMP install or go for Debian. Those will get you a very small installation footprint, but you won't have X by default so you'll have to learn how to do things from the cli.