Almost nobody understood my earlier webapp idea, so I'll try again. Imagine you were looking at a website such as FriendFeed and you wanted to create a near pixel-perfect copy but in a way that you could move things around, adjust shadows, etc. I want a tool that makes that easy.
Idea for a useful webapp: A tool for doing web page mockups that's better than Photoshop because things actually look right (because it's rendered by the browser). It doesn't need to generate good html, so absolute positioning, etc is ok.
Obviously I can't provide a lot of detailed plans and guarantees, but I can tell you that I'll do my personal best to ensure that the FriendFeed users and community are treated right. I love this product too, and don't want to see it disappear.