Lisp. 3D graphics. Compilers. Operating systems. Mobile devices. Cool stuff.
I use imaxima from Emacs to interact with the Maxima symbolic algebra system. imaxima produces nicely typeset output from the results of Maxima, instead of crude ASCII graphics, and also supports embedding plots and drawings directly in an Emacs buffer. imaxima works by running LaTeX on the output of each Maxima command you enter; it then uses Ghostscript to produce an image that is displayed in the output buffer.
I also use the Solarized color theme with Emacs, which I find quite easy on my eyes. However, there is a problem: imaxima output, which uses Computer Modern fonts by default, becomes quite hard for me to read: