Frank, a garden hero of mine, has put up an edible plant resource called The Vegetable Garden. It is filled with all sorts of edibles including a fair number of perennials. Check out the perennial brassica section! Not only is he generally knowlegeable about plant life, but he also has experience with lots of rare tubers including Oca, Yacon, Apios, and others.
Talking about perennial brassicas, another fellow gardener from Homegrown Goodness, has set up a blog called Perennial Platter and the first post details perrenial 'kale' Chou Daubenton. I've been looking forward to this as a resource for those interested in permaculture.