Assembly has fluid width, two columns, right sidebar, is widget ready, has valid XHTML, and is neutral in tone using metallic gray, steel grey, white, cream and features transparencies for depth and a modern look.
picoclean is a clean, elegant, minimalistic and fast theme.
Showcaser has a really clean and minimal design ideal for sharing photos and content online.
thetalkingfowl is a semantic, HTML5 minimal template with plugin-free flickr and twitter feeds.