Another D3-based, open source library is Contour:
<a href="http:&#x2F;&#x2F;forio.com&#x2F;contour&#x2F;" rel="nofollow">http:&#x2F;&#x2F;forio.com&#x2F;contour&#x2F;</a><p>Easy to implement basic charts like line, bar, pie, scatter, etc. and extensible with D3.