Well, the game is still alive and kicking, and is widespread on mobile devices. Caisses is one of the more interesting clones I've come across though, and provides amazing depth considering it's a piece of freeware.
Your basic aim is the same old story - you're a warehouseman who must shuffle parcels around. You can only push the boxes in a straight line, and you can't push more than one box at a time. As a result, the gameplay is very addictive, but certainly not very original.
The best thing about Caisses is the fact that you can customise the game to the n-th degree. Not only can you choose from a bevy of cool backgrounds, but there are loads of game themes to choose from too. For instance, you can choose to play as Pac-Man, Zangeif, a nurse, or even the Linux penguin, and the objects you push change accordingly.
It gets pretty tough as you progress through the 500 levels, so it would've been nice to see some kind of hints feature, but the challenge of getting your head around the hundreds of puzzles is enough to keep you coming back for more.
Great looking and infinitely customisable, I challenge you to find a better Sokoban clone for Pocket PC.