Sinizine: There's free and better versions of controller input software out there for anyone that would like to use controllers really.
Wishbone: Free, granted, but better? I'm not disagreeing, as I haven't used any of them, but I did research the features of a number of them a while ago, and it seemed to me that XPadder was by far the most advanced.
Can you recommend other free alternatives?
Motioninjoy is pretty good, aimed at PS3 controllers but works for general ones too. Things like GLOVEPie offer huge amounts of customization, though it's aimed more at games that offered no controller support at all. JoytoKey is also pretty popular, though I haven't used it myself. Heck, I think technically there are even freeware versions of Xpadder too, at least according to the product's wiki entry.