Implementations of the Archimedean solids plus a few other fun ones and an integrated better 3D rendering of them. Pens. Hobby curves.
There's also a lot of future-looking infrastructure here (see: "maker functions" in the release notes), a fair amount of clean up, performance, etc. Click the "browse" link for detailed release notes.
What's new? More geometric operations, integer sequences, complex functions. KML parsing. Chloropleths. etc. As ever, more tests, examples, bug fixes; a certain amount of refactoring.