How to concatenate icons into a single image with ImageMagick?

I want to use CSS sprites on a web site instead of separate image files, for a large collection of small icons that are all the same size. How can I concatenate (tile) them into one big image using ImageMagick?

convert works much better than montage. It arranges images vertically or horizontally and keeps png transparency.

convert *.png -append sprites.png (append vertically)
convert *.png +append sprites.png (append horizontally)

From the page you linked, 'montage' is the tool you want. It'll take a bunch of images and concatenate/tile them into a single output. Here's an example image I've made before using the tool:
_{(source: davr.org)}