Discovering new features

I work with a web-based platform with lots of data and various tools to view the data, perform analysis. Users are often impressed by one or two features and stick with them. The platform adds new features regularly; too many and too often for most users (and the sales team) to keep up. We have release notes that are emailed out and the occasional press release, but we're still in search of organic ways for users to discover new features.

One idea we had was a pop-up that included "Did you know?" text and some graphics. We know that most users ignore these. Has anyone been successful with popups like that? Or Are there other interfaces that have seen more success?