I prototype in Fireworks which works well in a process you have described. Not only can I output a working model, when we go to production I can optimize and slice out the assets. I do my own web building with a combination of Dreamweaver and hand coding with html and css. I also do actionscript with Flash and am starting to tackle Javascript. I spent 5 years designing GUI in an educational and gaming environment. Also with a background as an commercial illustrator I do excellent asset creation and am an exceptional designer.
I look forward to hearing from you