Pics.io - Pics.io is a cloud service that people can use to manage their creative content and files, collaborate with their peers on this content, and then share it with their clients. Read more about Pics.io.
Invision - Prototyping and collaboration for design teams
Google Drive to Slack - Slack notifications whenever you work on Google Drive docs
Visualtip - A service that allows designers and clients to annotate and collaborate on images in real time
Pastel - Sticky note-based feedback collection tool for live websites
Interappy - Interappy helps you get a handle on your Google Drive!