Darius Kazemi has built an amusing bot, the Amazon Random Shopper which, whenever it runs, buys him random crap from Amazon. Here is some of the stuff it bought so far.
Every time I run it, I give it a set budget, say $50. It grabs a random word from the Wordnik API, then runs an Amazon search based on that word. It then looks for every paperback book, CD, and DVD in the results list, and buys the first thing thats under budget. If it found a CD for $10, then the new budget is $40, and it does another random word search and starts all over, continuing until it runs out of money, or it searches a set number of times.
It cant spend over budget, because it has its own Amazon account, and I give it a gift card. Theres no bank account or credit card info so it can only spend whats on the gift card. As my friend Daniel Joseph put it: Here you go, child-bot. Have fun at the mall with the other bots. Dont spend it all in one place!