Ask HN: How to find ideas for SaaS products / B2B web apps?

Hey HN. I know the 'idea' topic comes up a lot here, but I'm asking this from a totally B2B perspective. I'm going with a market-driven approach on my next project, but I'm having trouble finding SaaS products that are needed. The only few ideas I have now are very general, like 37signals' products (group chat, project management) - but that's not really something I want to go up against for this project (although if I don't find anything else...). I'm not looking for new or unique ideas, I'll happily improve on existing offerings. Any advice on where to find pain-points or businesses in need of SaaS products?