Graphing tool
^2|x=y^3+3sin(y^2)-5y+4%3b=0.3)
I made a shiny thing! It can plot arbitrary functions of the form x=f(y) or y=f(x). Under the skin, it just massages its arguments and passes them through to Gnuplot. Here's the source code.
Update: now 48.3% even shinier - see on the right