Screenshot of the jsPlumb jquery demo
I've been using jsPlumb in a recent project to draw some fun visualisations in conjunction with meteor.js and my thoughts on jsPlumb are very positive. jsPlumb is fast to load, draw and redraw connections, it integrates with various different JS frameworks and it's pretty simple to use. About the only criticism I have is that it would be nice if you could influence the connection routing with a bit more precision, or simply have the ability to set up some elements that the connector should try to avoid.
Integrating the library with meteor.js was as easy as placing the jquery jsplumb plugin file into the client/lib directory of the project.