Might want to check out Plots.jl [1], which is pretty quickly becoming the de facto plotting library for many Julia users. It abstracts over various plotting backends, including native Julia graphics libraries like GLVisualize.jl [2] (which IMO has amazing potential for simulation visualizations once native graphics programming in Julia matures).
I hear the normal PyPlot/GR wrappers are pretty useful as well. They're ultimately not native Julia code, but since Julia makes it so easy to reuse tools in other languages, why not take advantage of that feature?