Skeleton is the only "sane" CSS boilerplate framework I've encountered. It's incredibly minimal -- the entire framework is so small and elegant that I can crank out websites without delving into the subtleties of the documentation. I find it really intuitive to use, and while I don't do a lot of web dev, when I do it's almost always with Skeleton. Anyways, I'm so glad you're working on Skeleton again! Congrats on the…
Semantic UI is really good as well. http://semantic-ui.com/
is semantic is not semantic, it's describing how it should appear.
You can break half of the examples page by just clicking everywhere and typing and such. I currently have three buttons stuck in the middle of their two positions, textboxes being broken, etc. It needs work.
Also it's rarely a good thing if your goddamn landing page makes an i3 stutter when rendering it. Doesn't really scream lightweight or efficient (although the biggest culprit is that background header video)