Plotting Arbitrary Julia Sets?

[Suffusion of Yellow]

Does anyone know of any Matlab (or any, really) program that will allow you to plot the Julia set of an arbitrary rational function? And hopefully have it look nice( I've found a Maple routine described here http://www.mcs.st-and.ac.uk/~jmf32/julia.pdfthat gives you ehhh looking ones, it'd be nice to have something more like http://en.wikipedia.org/wiki/File:Juliasetsdkfieldlines2.jpg)? All the other ones I've found so far kind of assume you're interested in plotting z^2+c and just change c.