Here is my extremely slow volume rendering solution.  It is based on placing a `Cuboid[]` for each voxel of the data. 

I switched from `MapThread` to `ParallelMap` as for some reason `MapThread` cannot be parallelized.

    slices = Import["https://dl.dropbox.com/u/3730003/slicedata.wdx"]
    data = Developer`ToPackedArray[Map[ImageData, slices]];

    (*downsampling slices*)
    resized = ImageResize[#, 64] & /@ slices;
    data = Developer`ToPackedArray[Map[ImageData, resized]];

    (*3D*)
    dims = Dimensions@data;
    coordswithdata = Table[{data[[x, y, z]], {x, y, z}}, {x, 1, dims[[1]]}, {y, 1, dims[[2]]}, {z, 1, dims[[3]]}];
    cubes = {Hue @@ #1, EdgeForm[], Cuboid@#2} &
    output = ParallelMap[cubes @@ # &, coordswithdata, {3}];
    Graphics3D@output

When I tried to rotate the view Mathematica crashed so here is an ugly screenshot, but it works (sort of)!

![screenshot][1]

    (*2D*)
    dims = Dimensions@data[[45]];
    coordswithdata = Table[{data[[45, x, y]], {x, y, 1}}, {x, 1, dims[[1]]}, {y, 1, dims[[2]]}];
    cubes = {Hue @@ #1, EdgeForm[], Cuboid@#2} &
    output = ParallelMap[cubes, coordswithdata, {2}];
    Graphics3D@output

"![Mathematica graphic](https://i.sstatic.net/UpIk1.png)"


  [1]: https://i.sstatic.net/IPhag.jpg