I recently launched Perligo, a writing feedback app. It's not a tool for crafting the content but rather a tool that allows others to provide line notes and general feedback in a self-contained, customizable interface.
Up until now, I've mostly received feedback from prose writers and poets, but I'm interested in those of you who are creating how-to books and other pieces of information products.
Just reply here if you're interested in helping me out. I'd like to see how much Perligo helps as is, understand how you get feedback now, and see if Perligo should be positioned for folks in your market.