DigitalLearn is offers free online refresher courses and classes on everything concerning IT - from Cloud storage and sending emails to Microsoft Office and social media.
Diigo is a research companion app - a web extension tool which is linked to browser activity, allowing you to collect and organise information as you research.
It also allows students to highlight, annotate, tag and save information, which is then accessible online from anywhere.
Doceri is an interactive whiteboard app for creation and presentation on the iPad (or Apple devices). It will also screencast content remotely.
Doodle is a digital polling tool which allows you to schedule events or activities by assessing which options work best for a large group of people.
You can also integrate existing calendars to enable better planning.
Dropbox is a cloud-based file storage application that allows you to back up data, documents, photos and more online.
Duck Duck Go
Search engine which doesn't track your activity online, promising less ads and spam, and quicker, more efficient searching.
Dvolver Movie Maker
DVolver is a free animation tool for creating and sharing short animated clips.