I have just found this amusing article about how some guys took more than a million and a half scientific papers from 776 different branches of science and came with the graph included in this post. You can find a larger version (5Mb) of it at this site. It shows how often papers from different disciples are cited by the same paper so it can give a measure of what fields are more likely to inspire interdisciplinary work.
Most of the research seems to be in Medicine and biochemistry (including all the -omics stuff). Math seems to be more unconnected to many other branches of science that I thought but to be honest I am not very sure about the methodology. More about it can be found in Mapofscience.com.