Keck Data Reduction Resources - PGPLOT

This is package put together by Tim Pearson for plotting. It makes, in my opinion, very nice plots. The downside to using it on its own is that is a set of functions, written in FORTRAN that must be called from either FOTRAN or C.
A number of languages have interfaces to this library, you can easily call it from Python or PERL for example. Tim Pearson gives plenty of examples on his webpage.

Tim Pearson has gone through a lot of work to make the installation of PGPLOT possible on a wide variety of computers.
He provides lots of details for Windows or UNIX

There are a couple of hoops you will have to jump through. I outline them on my building PGPLOT on the Mac.