This was a fun topic to research!
Here's a top ten list from a site called Sparkplugging.com :
After about an hour of searching, all the other resources I found had essentially this same list. Here's a link to another list of specific businesses you can "start in your pajamas" from Inc.com http://www.inc.com/ss/11-businesses-you-can-start-in-your-pajamas-2011
Some things to consider: Right now, your job is a place where you get to be independent, get good feedback and earn a good living. Is there a way that you could do what you do at work, but do it for others online as a consultant? Is there something that you're really into, like photography, for example, that you could make money at online? First figure out what you would LIKE to do, then think of a way to make it into a business.
This is an exciting idea...can't wait to see what you decide to do!