Duolingo - Duolingo is a free language learning app for iOS, Windows and Android devices. The app makes learning a new language fun by breaking learning into small lessons where you can earn points and move up through the levels. Read more about Duolingo.

Litmus - litmus tests and tracks your email campaigns, so you can always put your best design forward.

Mondly - Learn 33 languages in 500 bite-size lessons and 14 conversational modules.

Email on Acid - We make the send button safer. For every campaign, every message, and every inbox, Email on Acid has the time-saving tools you need to put your best email forward.

Lingvist - Lingvist helps you take your foreign language skills to the next level with a broad selection of exercises and lessons.

250ok - 250ok offers a SaaS-based platform to monitor and measure the deliverability of email networks.