Have a look at ProtonMail, a secure, privacy-focused email provider that you can use as an alternative to Gmail.
Mender is an open source tool for updating your embedded devices safely and reliably, over the air. This helps to solve the problem of updating embedded and connected devices.
Free Download Manager is a popular open source application but unfortunately, it is not available for Linux yet. But your vote can help bring it to Linux.
A new Linux project named XikiHub has been spotted on Kickstarter. It aims to add a social community feature right into the Linux command line.
If you are looking to find free and open source software, here are some websites from where you can download free software.