Consulting, Small scale manufactoring, porn( I have a friend form HS making several 100k a year in the porn industry) Small scale confections, machining, all kinds of sales, record keeping, RE stuff, raising "pets", and many many more...
The really question is can you legally do it in your area.
I have 2 consulting biz running right now, not making a bunch of cash, but its netting about 1500 a month for basicly what ammounts to less then 100 hours of work a month.