SEO, paid traffic affiliate marketing, infoproducts, SaaS, viral / social media-led stuff, paid blogging - those are the usual routes that spring to mind. Some cross over.
Good places to start learning:
"Four Hour Work Week", as mentioned, and Tim Ferriss' blog.
"The $100 Startup" - book.
Smart Passive Income - blog
Viperchill - blog
ProBlogger - blog. Ignore the guest posts, read stuff by the founder Darren Rowse.
Good places to start learning:
"Four Hour Work Week", as mentioned, and Tim Ferriss' blog. "The $100 Startup" - book. Smart Passive Income - blog Viperchill - blog ProBlogger - blog. Ignore the guest posts, read stuff by the founder Darren Rowse.