Ubuntu 9.10 only: Ubuntu Tweak, the all-in-one system modifier and software manager we've previously mentioned, has a new release out that improves the app installation process with a consolidated view, online app browsing and synchronisation, and adds a few other goodies.
Previous versions of Ubuntu Tweak have included a means of installing non-standard applications, but this 0.5.0 release consolidates the tools to do so and makes it a lot easier to navigate. Simply check off the apps you want to grab — and there are a lot of great ones here — or do so from the online app library, and sync it to your Ubuntu Tweak software. Elsewhere in the software, you'll find tools to customise your Ubuntu system's menus, icons, desktop, login window and other features.
There is, of course, nothing in Ubuntu Tweak that you can't do within the configuration tools and files of Linux itself. That said, for beginning users looking to avoid the hassle of repositories, authentication keys and config file editing, Ubuntu Tweak is a nice alternative. It's a free download, and this version only works with Ubuntu 9.10.