Software to draw illustrative figures in papers I would like to have suggestions of good software for drawing illustrations in research papers. I already know about Xfig, but this works only on Linux and is at times, clunky when it comes to text. Moreover the resolution is not always perfect making it difficult to manoeuvre the objects. Besides it is tough to learn and master, with all its weird click procedures. 

I would love to know about better alternatives. Not talking about graphs here, just block diagrams and explanatory illustrations.
A free, fairly portable, and very complete tool for general illustration is Inkscape. It uses SVG as its native file format, and aside from attempting to be a decent drawing tool in its own right, one of its design goals was to provide complete coverage of the features available in SVG.

For block diagrams, flow charts, and other simple sketches of process and data flow there is Dia. It's primary design goal is to duplicate the features of Visio in free software. Like Visio, it uses a stencils and connections drawing model that works really well for diagramming relationships and flow, but gets tedious when attempting to do art.

For clean layout of directed or undirected graph diagrams, it is difficult to beat the Graphviz tools. They are primarily designed to be used from a textual description (a concise intro here (PDF)) of the graph, but there are various GUI tools that can edit their .dot files.