In Ubuntu (Unity), the Super (Windows) key is used to open Unity Dash. Accidentally pressing the Super key when playing fullscreen games can be quite annoying, because Dash covers quite a bit of the screen, so you can't see what's going on, and it also switches the keyboard input from the game to Unity.

If you've gotten used to using the Super key to open Dash and don't want to change it, you can use a Python script, created by Sergiy Kolodyazhnyy for AskUbuntu, which automatically disables the Super key from opening Unity Dash, if there are any fullscreen windows. Note that the script has only been tested in Ubuntu 16.04.

The service is free, allows uploading files up to 10 GB in size, and it stores the files for 14 days. In my test, it was also very fast.

Old Linux kernels can take up a considerable amount of disk space. Apt ("sudo apt-get autoremove") tries to remove uneeded packages, including old Linux kernels, but it may fail to remove all of them.

Apt may fail to remove old Linux kernels when using an Ubuntu version that's under development, if you encounter THIS bug (which still occurs in Trusty), or if you've installed the kernels manually.

I recently stumbled on an issue with Dropbox and the Ubuntu flavors that support AppIndicators (except Unity), like Xubuntu and Lubuntu: the Dropbox AppIndicator icon shows up as broken and the menu doesn't work. This isn't a new issue though, and it seems to occur starting with Ubuntu 14.04.

The issue occurs with the Dropbox packages in the official Ubuntu repositories (called "nautilus-dropbox", which doesn't depend on Nautilus and can be used to install Dropbox on any desktop environment) as well as the Dropbox package downloaded from its official website. 

Lantern is a free, open source internet censorship circumvention software that was created to "give users fast access to the blocked Internet". The application is available for desktops (Linux, Windows, Mac) and Android.

Update: Lantern no longer provides free unlimited usage (the code is still open source). Now you get 800 MB each month, and to get unlimited data, you'll need to pay $27 (USD) for 1 year or $48 (USD) for 2 years (these are special launch prices and may go up).

Ubuntu 16.04 will be available for download in a few hours and since many of you will be installing it as soon as it's released, here are some useful things you can do right after the installation.