I think it would be really interesting to build a phylogeny of the world religions, in which each faith is a leaf of the tree. It could be done using the known historical events leading to the formation of different schools of thought or it could be done using dogma (i.e. monotheistic versus polythestic, written versus oral tradition, resurrection versus reincarnation, etc) as binary phylogenetic characers.
The first phylogeny based on known historical events would of course be accurate, and would allow creationists to face the historical contingency of their beliefs. The second phylogeny based on the phylogenetic method would be of interest in identifying homology, parallelism and divergence amongst the world faiths. It could be used to test my hypothesis that extremist islam and extremist christianity are sister taxa. In any case the trees would make great visual aids.
But I won't be doing it myself until they put religious data into genbank.