The Numerical Mathematics Consortium (http://www.nmconsortium.org) recently
posted a first draft of the "NMC Technical Specification." Skimming the
document, I was underwhelmed by its depth, but maybe it deserves some
attention.
Another thing: The "Poor Man's Integrator"
http://www-sop.inria.fr/cafe/Manuel.Bronstein/pmint/index.html
looks interesting, but I don't know anything about the algorithm.
Maybe somebody might like to translate the 95 line Maple program to
Maxima.
Barton