Except that it seems to be a dry winter here, I was considering getting two of the plastic troughs that one uses in wallpapering and simply setting my bike's wheels into them, so that water running off the wheels and downtube would be contained and I could still lean the bike up against the wall as usual... A length of plastic raingutter and a couple of caps to match would work, too. Sort of the same idea as jnoble's, but without the stand.
Of course, if it keeps not snowing ever, I won't need to worry about it.