These two forms helped a lot when it came to finding good questions to ask when developing a site. You could create a web based form from the two of these, customizing the questions to your needs...or make some print outs for the clients to fill in and for you to work with. I think you will find them both very useful.

http://www.wilsonweb.com/worksheet/pageplan.htm
http://quixoticproductions.net/planning_worksheet.htm