Ask HN: How to "sandbox" work and non-work stuff on the same PC?

I'm a freelancer that does a lot of work from home on my Macbook Air but I also use the same Mac for a lot of non-work, time wasting stuff (FB, twitter, surfing, etc).

My problem is that I'm not disciplined to stay in a "work" mode for too long. For instance while I'm working in XCode I might inadvertently open a new techcrunch or nytimes page and start reading while XCode is compiling. These brain context-switches are killing my productivity.

Is there some software solution that can create two virtual work environments for me? Something that can "sandbox" my work stuff and do the same for my non-work stuff?

OSX Spaces comes close, but doesn't do true segragation for my brain to "context-switch" into work/non-work mode. With Spaces the dock stays the same so I can easily click on some twitter client and start reading tweets. Also if I open new window on an app (Chrome) that's already open in a "non-work" space than it'll go back to that non-work space.

I feel something will work if it will require effort for me to open that time-wasting page. For instance if I use another computer strictly for non-work stuff then getting up and using that computer instead would do a "context-switch" in my brain to go into non-work mode. Otherwise it's just too easy to open a time-wasting app.

Short of getting another laptop (or an iPad) for non-work stuff, does anyone have any hints/tips/ideas on a software solution on how to really separate work from non-work stuff so that switching to non-work mode requires some kind of effort?