I don't think it's easy to start a project which will sustain you with minimal continuing effort. If it were, I'd have done it by now :-)

You have basically two options: A ground breaking new idea, combined with a good business plan, or you have to be so good at what you do that an occasional job earns you enough.

Even if you have a really good idea, it will take lots of dedication and effort - nothing that you do for a few months, in the hope that it will feed you for the rest of the decade.

Ideas? I have one, but I don't know if you can make money from it... anyway, here it comes: An anti-lock-in service.

Let me elaborate... there are a lot of "external" (ie ones I don't have control over) websites I have put lots of effort into: perlmonks, other discussion boards, my email provider (filter rules, settings). Many people also put much effort into social networking sites, online calendars etc.

What happens when one of those goes down permanently? Or changes its terms of service for the worse? (as happened with StudiVZ, a popular German student's social network) - Well, my contributions are lost. D'oh.

I'd like to have a service that lets me backup my online contributions to my local hard disc, and convert these backups to be usable for other, similar websites or programs. Turn that gmail profile into a thunderbird profile, google calendar to outlook, whatever. Keep it universal, easy to extend and easy to use.

I'd be willing to pay for such a service, and considering how much time we spend online these days I think it has a future. It's not easy to do, and perhaps not easy to sell - that's why I don't think it has properly be done before.