Ubuntu?
It's more polished (especially for a Linux newbie, probably) and current than Debian (on which it's based).
Almost any piece of software - including mySQL, Apache and Tomcat, is pre-configured and usable out-of-the-box just after first-time installation.
As with almost every Linux distribution, you need to install Sun Java manually but there are step-by-step Howtos on how to accomplish that.
Ubuntu's upcoming release Dapper Drake actually grants 5 years of software updates (which are more than easy to apply), it's already (Ubuntu's a quite young distribution) certified for mySQL, IBM's DB/2 and VMWare (just to show how sincere Ubuntu is about providing a most professional and reliable platform on servers).