I'm exploring Amazon FBA. Is not a success story because I'm still in the midst of it, but from what I'm seeing it is something that I can learn, my tech salary allows me to save for some capital and try that business.
Before this I explored day trading, which also has the potential to create money on the side. It does take a lot of training and risks...
Another option which I've done too is taking contracts, configure a server, update a website, etc.
Good luck!