WordPress Green is a two column, widget ready green theme.
Green Lush is a fresh, neat and clean two column theme for WordPress based on a Blogger Template by Yamasaki.
Cory has released RockinNewspaper 3 Column and RockinNewspaper for AdSense.
jquindlen has released QNight and DeepBlue.
Minimilistica is a three-column, primarily one-column, completely minimalistic theme. Very lightweight and completely customizable through an admin panel. Supports WordPress Widgets, Gravatars, ZooomrRSS, and FlickrRSS by default.
Jammed and Green is a two column, clean and green theme.
YGoajx is a simple 3 column elegant theme loosely based on the principals of web 2.0 and enhanced by Ajax.
Lot of green themes! I guess Spring is in the air. :o)