All Artwork by Koji Kumeta.
"Sayonara Zetsubou Sensei" is a gag manga by Koji Kumeta and pretty much my favorite manga. Part of Kumeta's unique style are the full-body-drawings of the protagonists every few pages. This tumblr blog is devoted to these drawings.
"Sayonara Zetsubou Sensei" is published in English by Del Rey or you can get fan translations at Suimasen Scans
I get the scans from different sources, so the quality might not be consistent.