LibreOffice Fresh

Latest stable release of the LibreOffice office suite. This is an official PPA provided by the Document Foundation.

To add this PPA to your system:

sudo add-apt-repository ppa:libreoffice/ppa
Proposed Kernel

This PPA contains the proposed kernel images for various Ubuntu releases, allowing you to get newer kernel versions. Normally you could have installed those kernels from the proposed update channel, but if you just want the kernel (not all the other proposed packaged that would break your system), then this PPA is for you.

To add this PPA to your system:

sudo add-apt-repository ppa:canonical-kernel-team/proposed
Grub Customizer

If you want to customize the GRUB screen of your system, either by look & feel or changing the boot settings and order (E.g booting other systems by default), then this tool can help you.

To add this PPA to your system:

sudo add-apt-repository ppa:danielrichter2007/grub-customizer
Boot Repair

Very useful tool to install on your Ubuntu's USB stick in case of boot issues. It simply repairs your GRUB bootloader on your hard disk and tries to make all installed systems on your disk bootable. If it fails, it can generate a log file for you to share. Offers advanced options.

To add this PPA to your system:

sudo add-apt-repository ppa:yannubuntu/boot-repair
elementaryOS Stable

You can use this PPA to install elementaryOS software on your Ubuntu/Mint installations. Packages include the Pantheon desktop shell, AppCenter, elementary icons & themes, and many other more packages.

To add this PPA to your system:

sudo add-apt-repository ppa:elementary-os/stable
Firefox ESR

Stable Firefox releases for enterprises. Those versions of Firefox usually receive only security updates, so they suffer less from the code changes or added/removed features.

To add this PPA to your system:

sudo add-apt-repository ppa:mozillateam/ppa
Firefox Beta

If you want to test the new features of Firefox using the beta channel, then you can add this PPA.

To add this PPA to your system:

sudo add-apt-repository ppa:mozillateam/firefox-next
Firefox Nightly

Daily builds of Firefox, contains the latest tests and features in Firefox browser.

To add this PPA to your system:

sudo add-apt-repository ppa:ubuntu-mozilla-daily/ppa
Updated Open Graphics Drivers

Bleeding edge updates for open drivers such as Intel (directly from Git). Also contains other graphics libraries updates. Adding this PPA can result in login issues and system issues, and removing it doesn't usually work easily, so add it on your own responsibility.

To add this PPA to your system:

sudo add-apt-repository ppa:oibaf/graphics-drivers
WebUpd8

PPA containing a lot of useful applications that are mostly updated to their latest versions.

To add this PPA to your system:

sudo add-apt-repository ppa:nilarimogard/webupd8
Lubuntu Unstable

Daily builds of Lubuntu software and packages. Mainly featuring the LxQt desktop interface along with its libraries. Remember: Those are unstable daily builds.

To add this PPA to your system:

sudo add-apt-repository ppa:lubuntu-ci/unstable-ci
Xubuntu QA Experimental

Daily builds of Xubuntu various packages, such as Xfce4 and Thunar. Those packages are not stable, and shouldn't be considered so.

To add this PPA to your system:

sudo add-apt-repository ppa:xubuntu-dev/experimental
FreeCAD

Latest stable release of FreeCAD; An open source 3D modeler software (alternative to autoCAD).

To add this PPA to your system:

sudo add-apt-repository ppa:freecad-maintainers/freecad-stable
Inkscape

Latest stable release of Inkscape; An open source professional quality vector graphics software. This is an official PPA.

To add this PPA to your system:

sudo add-apt-repository ppa:inkscape.dev/stable
Shimmer Project Daily

This daily PPA contains the latest versions of the Xfce/Xubuntu themes and icons. It also contains an icon set for LibreOffice. You can safely add it to your system.

To add this PPA to your system:

sudo add-apt-repository ppa:shimmerproject/daily
OBS Studio

OBS is a professional broadcasting software that works on Windows, macOS and Linux. It allows you to do powerful screencasts.

To add this PPA to your system:

sudo add-apt-repository ppa:obsproject/obs-studio
Handbrake

HandBrake is a tool for converting video from nearly any format to a selection of modern, widely supported codecs.

To add this PPA to your system:

sudo add-apt-repository ppa:stebbins/handbrake-releases
Lutris

Lutris is an Open Source gaming platform for Linux. It installs and launches games so you can start playing without the hassle of setting up your games. Get your games from GOG, Steam, Battle.net, Origin, Uplay and many other sources running on any Linux powered gaming machine.

To add this PPA to your system:

sudo add-apt-repository ppa:lutris-team/lutris