I've tried lots of things but haven't finished any.
codexon: You are not focused.If people gave up after one or two failures, nothing would get accomplished.- Wrote a program to model the stock marketEveryone wants to do this, but unless you have insider information like Goldman Sachs or some rare mathematical insight that a million PhDs have overlooked, you are likely to fail. The stock market is a zero-sum game where most of the profits go to the high end of a Pareto distribution. This is too ambitious for you.- Worked on a paper with a professor.Unless you are a genius, I doubt any of these professors would be working with you seriously instead of just being free lab labor. Your knowledge is most likely too shallow to be useful in high-tech research that gets all the grants. However, this might be your goal if you want to go to grad school.- Tried to start a company over the summer.Keep trying.- Applied for X internshipsYou are too young. There is also a recession so you can lower your expectations.- Half a dozen math/science contestsThere's something wrong with your plan if you have the time for half a dozen of them.- Tried to start a blog, worked on it for two years.Link?