interwebs and books. - beware the books that concentrate solely on debt, or selling you shit, there are tons more of those then actual good information.
mutual funds have load rates, generally these load rates can eat into your returns, and with everything being in flux an index fund ( computer controlled) may eek you out a point or two more.
something relatively stable seems to be peer lending, the issue is it locks up your money for a fair bit of time as dumping the loans is a risk on what you can get out of it.
aside from the old standby drug dealing, starting a business or investing in your own skills, atleast at first, has always paid off more for me then investing has.
There are some interesting options to be had if you can come up with 25k+ and get around the pattern day trader rules on small stocks, but its quite risky.