Readwise

Readwise pulls together highlights and notes from wherever you make them — Kindle, articles, PDFs, other read-later apps — into one place, and then resurfaces them periodically so ideas you found interesting weeks ago don't just disappear into a folder you never revisit.

For a newsletter writer, that resurfacing habit is the useful part: a lot of good issue ideas come from something you read and half-remembered, and having those highlights come back around on a schedule makes it more likely you actually turn them into something rather than losing them entirely.