Drawing Directed Acyclic Graphs: Minimizing edge crossing?

Question

Laying out the verticies in a DAG in a tree form (i.e. verticies with no in-edges on top, verticies dependent only on those on the next level, etc.) is rather simple without

Answer 1

Dot seems like it would fit the bill:

dot - ``hierarchical'' or layered drawings of directed graphs. The layout algorithm aims edges in the same direction (top to bottom, or left to right) and then attempts to avoid edge crossings and reduce edge length.

https://docs.google.com/viewer?url=http://www.graphviz.org/pdf/dotguide.pdf