Extra Cash

Nigerian Princes. ROIs are amazing.

Use the search bar. There have been a ton of questions like this. Check out the posts/threads by @"thebrofessor" for some of the best content related to personal finance.

The only place liquid enough that can provide an okay return is in stocks. Buy a dividend paying company with solid free cash flow.

Girl Scout cookies. Just opened a new distribution channel.

Assuming you are being serious, you are probably better off simply tossing it in a checking account/money market fund and call it a day. Set a liquidity number you are comfortable with and once you hit that then put any excess into the market.

Personally, I don't consider stocks a place to put money that you need to be liquid but naturally everyone has their own risk tolerance, etc.

You should buy lots of beer with the money.

This one time I was at WalMart and PBR was on sale for $2.50/6 pack. I decided to buy three gross worth of it. It was tough to stick into my rusty Honda and nobody could stick their jackets in my closet for a year, but I bought 432 cans of beer for $180. That's a savings of $250!!!

Just look up high yield savings accounts on the Googlez. You can get nearly 1% at certain banks, like Ally or GE Capital. This is not rocket science and I fear for you if you can't figure out something as simple as this on your own.