Kimi ga nozomu eien (The Eternity You Desire); This series is based off of a Japanese visual novel adventure game released back in 2001 for pc in japan. A game which you play as the main character seeking companionship/friendships with the other characters. This show is based off of the Mitsuki/Haruka scenarios.
I highly recommend this drama/romance series to anyone who likes animes with real life situations. Even if you aren't into drama; this show will not disappoint. Right off the bat it seems like a run of the mill Harem/comedy, but that soon changes after a devastating tragedy.
Season 1:
http://www.ani-watch.net/2008/06/kimi-ga-nozomu-eien.htmlSeason 2 "Kimi ga nozomu eien: Next Season" : This series isn't complete yet but is a 4 episode Ova. It is based off of the Haruka Suzumiya scenario (do not watch it 1st, it contains spoilers for the 1st season.)
Akane maniax: A spin-off of the original series, based on Haruka's younger sister. I haven't seen this yet, so I won't recommend it.