This is a cool collection of graphs of relations using software called GrafEq:
http://www.xamuel.com/graphs-of-implicit-equations/
For example, at the right is the graph of
.
There are several other cool graphs displayed here.
It is worth noting that Wolfram Alpha can graph these relations, too. For example, here is the above equation:; while Wolfram Alpha captures the spirit of the graph, the image is not as detailed or attractive as the GrafEq version.