Well there are hundreds of get rich quick scams that you might consider... but don't. They are a waste of time.
However, if you are looking for a legit way to earn some real money there is definitely work available online.
First of all, how much extra cash are you looking to make? eBay is a very legit and profitable way to earn some extra cash if you find a good niche.
Otherwise if you want to be a bit risky you could try putting some money into the stock market, but that's certainly not a job and certainly not guaranteed to work for you. In fact you could lose all of your money if you aren't careful.
What do you like to do and do you have any computer/internet skills that you want to put to use with an online job?