Google launched the Add-on store today for Docs and Sheets, which basically gives you apps for your documents. The Add-on store has tools made by third-party developers (and a few Google originals) that you can install to add features to documents and spreadsheets that weren't available before, like creating labels or sending customized emails. The feature resembles the Google Play Store and currently features about 30 add-ons.
This is a way for Google to enhance Docs and Sheets with some of the features that are mainstays in Microsoft's Word and Excel programs. One of the launches is an add-on from Avery Label Merge, which lets you merge data from a Google spreadsheet into Avery address labels. Mailchimp's add-on lets you choose different templates and make customized emails, and then send them from directly within Google Docs.
And then there are some unexpected add-ons that could prove to be really useful. EasyBib’s Bibliography Creator lets students look up academic sources, and then create and insert citations into a document in MLA, APA, and Chicago Manual of Style formats. UberConference also released an add-on that lets you invite people via email to a voice conference call from within a document, letting a group edit that document all together. This isn't the first time Google has opened up Drive to third-party developers, but these are the first app-like programs specifically for documents, and they could add enough new functionality to encourage users to convert from other services.
Google says it will put more add-ons in the store as it approves programs that developers have submitted.