I read on the interwebs today about a guy who was inspired by this XKCD comic about a guy who sets up a script that buys a $1 item off ebay every day for a year. He's gone and written something that effectively does this, except it has an allowance and gets given a $1 a day which it can save up or spend it's budget on stuff.
This got me thinking about making something similar that scours Amazon for cheap Blu-ray movies (sci-fi by preference) that are eligible for free shipping. Except I realised pretty earlier on in my thinkings that I could never automate this as it would no doubt buy multiple copies of the same thing as the various special editions came out and also there are some (sub)genres I don't much care for - like horror - that I wouldn't want it buying either.
Grabbing some test data and doing a few sums proves that it should work and end up ordering a new movie every week. Of course the big question, is should I actually go through with this crazy plan? :)