[DarkMaster]

Here's a nice description.

EVANGELION, certainly one of the most popular, and arguably one of the best animes ever produced, is one of the rare sci-fi series that actually follows through on the ambitious themes and ideas that it presents. The series is set in the year 2015, fifteen years after what was supposedly a meteorite struck Antarctica, wiping out half the population of the Earth and leaving the rest to contend with rising sea levels and to figure out exactly what happened. Chief among the mysteries is the arrival of the Angels, an alien race who are possibly responsible for the subsequent attacks on Tokyo.

It's very philisophical and psychological, as well as controversial, with heavy religious themes and references (or so I'm told, from what I've seen of the series so far, that does indeed appear to be true). Basically there's these synthetic organisms called Evangelions (those mecha things). This organization called Nerv is using them to battle against these alien creatures called Angels. The pilots are quite young (main character is 14 I believe), and they are picked to pilot an Eva based on a certain telepathic connection which they can share with an Eva (Eva's must be controlled this way, not your ordinary mecha being thingy).