I am a recent college graduate, and have a stable job now. I do not waste my money on useless things, so now I have a decent amount saved up (around $50,000). I noticed that my money is just being saved. Is there something I should be looking to invest in?
First, of course, I agree with the comments about paying down debt. Then reserve some of those savings as an emergency fund.
After that, the default answer is to invest in an index fund as Mr Belford suggested, such as Vanguard's total stock market index fund, and leave it there forever. Even when the market tanks -- especially don't sell it when the market tanks! I might leave some cash in reserve so I can buy when the market corrects/tanks and stocks go on sale, but I'm paranoid that way. (Pick 5 random people and you'll hear 6 contradictory opinions on where the market will move soon.)
I personally would just park it in the index fund. You just graduated; you have so many things you could spend your time on (building career, socializing, learning kickboxing and sailing and rock climbing and woodworking and intramural soccer and.....), and landlording has the potential to become a time sink.
On the other hand, if you're really into landlording, why not. Just be aware it's a lot more complex than pay $50k down and collect $500 in easy profit each month. There's a lot of learning to do before jumping in.