Talk to people who work in large businesses. Ask them what troubles them. Ask them what their bosses complain about. Look at successful existing SaaS apps (inc

Talk to people who work in large businesses. Ask them what troubles them. Ask them what their bosses complain about. Look at successful existing SaaS apps (including 37signals', which are not by any means perfect) and see if you can't make a "quanta" of improvement. Talk to the people who gripe about the product and build what they wish they had. There are no easy solutions here - just a willingness to ask questions and a quest for making things more useful and convenient.