The Master of Illusion downloads allow you to perform magic on your DSi to amuse yourself and friends, so if something like that amuses you, these might be worth checking out. Shuffle Games, though not the most complex trick of the lot, is an easy to learn group trick that's good if you want to amaze your friends, but could be figured out by sharp-eyed volunteers. Vanishing Card might be worth showing to others, though it's easy to figure out, but again, if you're just looking to baffle someone real fast, it's not a bad addition here.
All of these tricks come from the retail version of Master of Illusion, mind you, so if you own that, you don't need these, and if you're a fan of magic tricks, you might be better served buying that instead. Shuffle Games is a simple, easily learned and performed trick, and of the lot it's probably the best bet for the lazy magician.