WVSundown created this awesome Tater Tote instructable. Although they're designed for potatoes, I'd bed these babies would probably work for anywhere you wanted to use a homemade grow bag.
If you want something with more structure, check out Cassandra's (aka apachebow) potato bin setup on youtube. I couldn't find the link for the all-natural fertilizer that she mentions but you get the idea.
We tried another variation on this theme at our house. I bought organic potatoes from Earth Fare and cut off the developing 'eyes' with a little piece of the potato to anchor them. I let that dry out a couple days and then planted my seed potatoes in homemade denim growbags the fashionista sewed up for me. I grew them in Eliot Coleman's organic soil mix to start them off. Our seed potato baby bin was set inside of this semicircle we pieced together using the leftover pieces of plastic chicken wire (they sell rolls of it at Lowe's) and layered the with whatever straw was on hand at the time. They're doing quite well. Hope you are inspired to grow your own potatoes.