This website provides resources that can aid in the assigning NMR proton shifts, IR peaks and mass loss in mass spectrometry. The original site is in German, but most (but not all) the content is translated on the English version of the site. From the left hand menu under Spektroskopei-Tools choose Wizards. From here you can enter a chemical shift in ppm and the NMR tool will identify likely protons and environments that could cause the shift. Enter a mass and it can identify likely mass loss sources. Enter a frequency in cm-1 and it can tell you likely functional groups that could cause an IR absorption. It is a useful tool for those interpreting IR, MS or NMR spectra.