Install rss-glx by means of the package manager of your distribution or compiling it from source and try some screensavers (for example Skyrocket or Solarwinds). Check if you can play the screensaver (and/or if you can play it smoothly)

Try to enable compiz

First, make sure you know how many sound devices your computer has. If your computer has only one sound device, you can just try to play a music file or use an application which has music in the background. If there are more than one sound cards in you computer, you should test each of them separately by using the sound configuration application of you distribution. For example in Trisquel 5.5, you can find it in the System Settings menu. Form there, go to the hardware tab and test each sound device by clicking the Test Speakers button.

Install and test fprint.

Install and test guvcview.

For Trisquel users:

$ sudo add-apt-repository ppa:pj-assis/ppa 
$ sudo apt-get update
$ sudo apt-get install guvcview

Git

git clone git://git.code.sf.net/p/guvcview/git-master guvcview 

For other GNU/Linux users, download the source code from the above website.

Install and test Simple Scan.