are they on Island or off
all Island censuses are indexed - buy them from Brian Lawson - there are many other useful indices (free) on Brian's site (burials,wills, non-CofE marriages/bapts), marriages post 1877)
Join the IoMFHSoc + buy MI's etc - though for one-off look ups this MB will normally find someone with the info. I doubt if many other places are as well served - added to which is the virtually complete Mormon filming of most major sources.

Off Island then you can now buy CD Roms with images of most county censuses - around £25/cd rom seems to be going rate