WordPress Green is a two column, widget ready green theme.
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.