I scribble a very rough sketch on a notepad. Once I have a reasonable idea of the layout and functionality of a page, I just move right into rails and iterate f

I scribble a very rough sketch on a notepad. Once I have a reasonable idea of the layout and functionality of a page, I just move right into rails and iterate from there. You get realism and real code that way. Moderate proficiency with XHTML/CSS makes iterating not that much more difficult than pen and paper. I remember reading that 37signals does all their mockups directly in XHTML/CSS.