This cool little antquarium can give you some desktop entertainment. all you need to do is place some ants on the gel surface, and watch them make intricate tunnels. The gel is not toxic and actually contains all nutrients ants need to live. So basically you're putting them in a bit edible cake!
I found this slightly weird antquarium on a trip to Amsterdam, which is as I recently discovered a great place for cool gadgets and weird-but-useful things. If you happen to be in Amsterdam, or anywhere else in Holland, the store that carries this neat looking ant aquarium is called "Expo". They generally carry slightly off the beaten path stuff, but you will not find too many electronics at this store, except for really strange (alarm) clocks and some other house hold items.