For sure there's some software you'll want just to have.
ubuntu-restricted-extras - this is for mp3's and flash and stuff like that.
openjdk-7-jre and icedtea-7-plugin - if you want java support.
Then some others that you might like.
rhythmbox - my favorite music player
vlc - my favorite video player
geany - favorite code editor
asunder - rip cd's
bleachbit - for cleaning unneeded files
gufw - a firewall if you want it
deluge - my favorite bittorrent client
fortune-mod - display fortunes via command line
You can look at these in the software center and install them or you can install them on the command line. To install packages you use `apt-get' and the arguement `install'. Because it need root privelidges, you use sudo, which is S uper U serDO . The super user is the root user, but you can't use that account like your own, it's only there for `administration'.
So the command all together would be
But you need to tell it which packages too so it really is
sudo apt-get install
you can update and upgrade packages too using this method. Using
sudo apt-get install package-name package2 ... packageN
#and to remove
sudo apt-get remove package-name
sudo apt-get update
sudo apt-get upgrade
To view the manual page for a command use the man command.
I recommend at least skimming the apt-get man page.
Best of luck with Ubuntu/Linux. Welcome to Ubuntu. If you want more information on using the Ubuntu desktop, go to the dash and type help and press enter. If you don't know what the dash is, press the windows key, or command key if you're on a mac.
And just for fun, the Advanced Bash Scripting Guide. Its pretty useful, at least after you've learned a lot of it.