Video and audio

Like in Windows, good video players are excellent audio players too.
What are the best video players in Ubuntu? SMPlayer and VLC are well known players, excellent and sufficient, low on resources and trustworthy. The former is able to search for subtitles and download them.

A specialized software to do that with subtitles is SubDownloader.

Audio players - well, if you just need an audio player that is simple and good (although VLC and SMPlayer are perfect in that role) I use Aqualung, Audacious or Qmmp. Few others are like that.
Most recommended out there are either not good, either too bloated: they are  trying to administer media libraries but are far too heavy . It's the case with the most used and recommended, like Amarok and Rhymthmbox.
I cannot see the point in using a lightweight OS like Xubuntu and installing such heavy applications who do nothing more than access the media library and the internet without ever getting closer to the power of Foobar2000 in Windows. Amarok installed on a 1gb ram PC with Xubuntu has good chances of becoming the heaviest application on that PC. Other less bloated audio players like Guayadeque, Exaile and Banshee are as good (bad) as Amarok and Rhymthmbox in accessing media library but not enough for me: I need direct access based on criteria set by me, not by the player. And I set my criteria by the directory structure of my music files. For a player to become acceptably heavier, it needs to provide supplementary benefits. And these big bloated players ARE NOT. So, they are UNACCEPTABLE.

Beside being simple and good in rendering music, a player has to display music in a proper way in multiple tabbed playlists.
Audacious and Aqualung are able to do that.  
I also need access to my music library. A music library is basically a collection of audio files in different directories and what I need for handling that is a FILE BROWSER INTEGRATED INTO THE MUSIC PLAYER. All that bloated players are unable of doing that, but instead access the files according to supplementary criteria that may be useless in some cases. What's the point in seeing music by the name of the album when you have thousands of them and too various to judge them together (I mean, when I listen to Bach and also to some music composed and played by friends of mine) ? What I need is direct access to my files, already ordered by directory structure,  and, just like in Windows, there are few players in Linux that do that simple task of accessing media library by folder structure: what I need is that Music File Browser! (The ideal for me is Foobar2000 with the "facets" add-on - but in Wine it has some issues that makes it less elegant that in Windows.)
So, I found some players that more or less achieve to do that.
Quod Libet behaves honorably, has a built-in browser (that you can disable) but the context menu of the browser is very limited and ... no multiple tabbed playlists - so this player is disqualified by a previous  more minimal criterion. 
Clementine.  It is much better: has file browser and tabbed playlists - which is all I need. The problem is JUST THAT: Clementine has a lot of other features useless to me that make it a little more heavier and that I cannot disable: access to internet services that I do not care about, Amarok&co-style display of media library (absurd), a search field that doesn't work, and a horrible orange fruity icon (with the interesting ability of squeezing out of juice in the tray as the file is playing). But people might like just that features, and so Clementine beats Amarok and Rhythmbox  even in those categories that I don't care about: people that don't agree with me and have different needs might  nevertheless chose Clementine against that bloated stuff. The sound quality seems excellent and I would not complain if I wouldn't have found a better player for me: it comes by the odd name of DeaDBeef.

I heard a lot about DeaDBeef from Foobar2000 fans (ex-Windows convicts) and after I succeeded installing it (that's how you do it) I was not disappointed. You can download a few plugins from the website. The most important is, of course, the file browser. Plugins have the .so extension and you have to open the file explorer (e.g. thunar) in root (gksudo thunar) and put these files in /usr/lib/deadbeef folder (or not anymore: now in /opt/deadbeef/lib/deadbeef). It looks like Deadbeef is able to convert and tries to recreate the Foobar2000 experience in Linux.

In fact the whole subject here is to find a player that would convince me NOT to use Foobar2000 in Wine when I access my music library.

Lyrics viewers: OSD Lyrics and CoverGloobus
sudo add-apt-repository ppa:osd-lyrics/ppa
sudo apt-get update
sudo aptitude install osdlyrics

sudo add-apt-repository ppa:gloobus-dev/covergloobus
sudo apt-get update
sudo aptitude install covergloobus

Video editors: Kdenlive
sudo add-apt-repository ppa:sunab/kdenlive-release
sudo apt-get update
sudo apt-get install kdenlive

To record radio - see post

To record sound in a simple way - this post