msc2svg is an open source software written in java that generates good looking message sequence charts in SVG format from a text file (see Example). The advantages of msc2svg are:
the simplicity of the description file. changing a part of the chart results in a lot of redesign and alignment work, if you do this in a graphic program. With msc2svg change what ever you want in the description text file and recreate the complete chart in few seconds. msc2svg helps you create the main part of your charts. You can continue editing them professionally with any vector graphic program like Inkscape for example.