The best way to push your hardiness boundaries is to provide tender perennials like figs with a warm and dry microclimate.  One grower I know planted his fig right under the dryer exhaust vent, with very good results, and others recommend locating your fig on the southern side of a house.  Stone patios can grab the heat from the winter sun and radiate it back out at night, and presumably locating a fig near a large body of water would serve the same purpose.

If you dry your clothes on the line and don't have a patio, you can still get figs through zone 6 winters with a little extra effort.  One option consists of cutting the roots on one side of the tree with a shovel to allow you to bend the whole tree down flush with the earth.  You can either dig a trench and bury the branches underground, or simply top them with bales of straw.

The alternative we've used involves autumn leaves insulating the aboveground growth of the fig.  My method worked okay, but the leaves got beaten down by rain and snow, and any branches that ended up exposed died back.  This winter, I'll probably take the advice of more experienced fig growers and tie the limbs together, pack in leaves, then wrap the leafy insulation with a tarp or other waterproof layer.

A final option, especially handy for those in the extreme north, is to treat your fig as a potted plant.  The fig can spend the summer outdoors, then once it drops its leaves (usually after a light frost), you take the plant inside to a cool basement or root cellar.  Alternatively, if you've got a warm, sunny window that's not already full of dwarf citrus, you can keep a potted fig growing all winter by bringing it in before cold weather hits.

I'd be curious to hear from those of you north of zone 7 who have had good luck growing figs.  Which varieties did you choose and how do you get them through the winter?  What kind of yields have you seen?