If I really knew the answer to this question, then I would take Eric’s advice and start an ISV. But I think that I have a pretty good handle on “What will people like me buy?”
E-mail was the first consumer killer app of the internet, I think that RSS will be the next. There is a market for news readers, but they need to be tied to email so that consumers can treat articles as a new flavor of email. And I think that ad-supported and paid subscriber RSS feeds are inevitable.
Digital devices are proliferating in my life. My computer is the hub that pulls it all together. I think there is an opportunity for personal digital asset management like iView Media. And I think there is a market for the fotolog as photo album - not for the internet, but as a personal travelogue on hard disk or CD.
And with device proliferation, I think there is a market for data storage transparency so that data can be accessed from multiple clients. I didn’t realize how useful this was until I started using IMAP email via fastmail, I would hate to go back to a POP based solution.
Finally, the computer has become a bigger part of people’s lives. Both Microsoft and Apple cater to the business market and have made their OS’s more professional. I think there is an opportunity for software that makes computers more fun. Xounds is a good example. It might drive me crazy at the office, but it’s good fun at home.