Where should I invest my money?

I am 25 and have an extra 2800 USD per month that I want to invest somewhere. I don't have any high interest debt. I already have my 401k maxed out. I have also been putting about 1000 dollars bi-weekly into an investment account, but I have lost money due to lack of experience in investing in the stock market.

I already have tried peer to peer online lending. I have had a lot of success with it, but I can not put any more than 2500 into it until I can save up more money in other places.

I would like an investment that is extremely short term(about a six month - one year turn around). It doesn't need to make a lot, but letting it just sit in a savings account and make .1% interest seems like a waste.