1- As a heuristic, find an existing successful product (for example invoicing, accounting, crm...) and tailor it to a smaller national market (for example France, Germany...) or to a specific niche (accounting for trainers, invoicing for plumbers...). That should give you a lot of ideas!

2- a tool to conduct online interviews. Right now when recruiting companies use a phone screening before flying the candidate in. By conducting an interview online, you can (for example) have him code the solution to a problem in real-time, how he thinks about it etc. So much more efficient than phone interviews, and a much better predictor for candidate quality.

3- a service to outsource video making for webapps. people making webapps often need demos of their products, but would rather not spend valuable time learning how to make a video, voiceover etc.

There would be a lot more. Ideas are a dime a dozen :-)