Here's an Startup/SaaS idea to try out:
Ever heard of the swiss army knife that is Pandoc? It can convert and reformat just about any document into another document.
Pandoc is amazing -- look at the insane generated map of input to output formats.
💼 🧠 Build and offer Pandoc aaS for enterprises and individuals
Build and offer Pandoc aaS for enterprises and individuals
This is a no-brainer service -- most people don't know this exists, and I'd argue most developers don't even know this exists (until they search, then all roads lead to Pandoc for document conversion).
Search for "pandoc online", though, and you get just about nothing.
It's not rocket science -- build a service that makes it easy to convert documents using pandoc. You could build this service in less than a day and launch it to HN (for a start), especially if you use providers for the "hard" parts (uploading documents, launching pandoc processes).
The hard part of this idea is probably getting the SEO juice up enough to rank first for "document convert" online or "pandoc online" or some such search. Use Google trends to your advantage.
There are a lot of juicy integrations and enterprise value to explore (think context menu integration in Google Docs/Office 365/etc), so let your mind wander.