Paper trading is the simulation of stock trading using imaginary money. For example, investing a hypothetical $50 in a stock that's worth $0.20 on Monday but grows to $0.30 by Thursday, would lead to an imaginary growth of $18.75. Paper trades assume buying and selling commisions are set at 5%.
Build a console, GUI, or web app that allows a user to invest $200 into any ten stocks that you pull from a financial/stock API. Display money lossed or gained if they had bought that stock a month ago and held it until the day they used your application.
For this particular problem, it is difficult to find reliable APIs. Here is one of the best we've seen.