I've just started using Along For The Ride (AFTR). This is an interesting approach to increasing traffic to your site. You'll see the widget on the right sidebar of this blog - if you mouse over it, then after 3 seconds a mini-window opens up with the site of another member of AFTR (this is done on a rotational system).
It's as simple as that. If you have the widget on your site, then the visitor doesn't have to leave it to view the other site, nor do they have to click on anything. Your blog is available in the same way on other members' sites.
I've just had it for a few days, but have already noticed a steady increase in traffic. I'd recommend checking it out here.