Cirrus is an Android client for ownCloud, a file sharing server that allows users to control and secure their own data. The application is a fork of the original ownCloud Android application (GPL) and offers some extra features like Material Design UI, search option in current folders, and the ability to switch between list and grid views.

One of the best things about Cirrus is that it is completely free to use and has no ads. The app is available for download on the Google Play Store and the source code is available on GitHub for those who want to contribute or customize the app. If you're looking for a secure and easy way to access your ownCloud files on your Android device, Cirrus is a great option.