First off, this is inspired by a post by a fellow I'm assuming prefers to be known as Brent Roos.  It's an excellent tutorial for installing Flock on Ubuntu, and I only decided to make this tutorial after noticing a couple different steps required for installation on Xubuntu. 

As of today, there still isn't a .deb for Flock, the very excellent browser that I'm using to post this very blog, so you'll want to download the archive from the flock homepage.  As of this writing the file is flock-1.1.1.en-US.linux-i686.tar.gz

Now open up a Terminal and browse to where you've downloaded the archive (it may well be the Desktop)
cd Desktop

Now proceed to unpack it into the desired location; I'll use the /opt location since it's good for this purpose.

sudo tar -C /opt -xzvf flock-*.linux-i686.tar.gz

Now we make a symbolic link in the common user binaries directory:

sudo ln -s /opt/flock/flock /usr/bin/flock-browser

But wait! Why did I add the -browser to the end of that link file, you may ask.  Well you can try it without, but if you do you'll find that the command flock already exists in /usr/bin.  It's a command from the util-linux-ng package that's installed on a default Xubuntu installation, so far as I can tell. 

Before we can use Flock we need to satisfy a dependency.  Xubuntu, in keeping only to the absolutely necessary, doesn't include libstdc++5 in a base install.  Since Flock needs this, let's install it:
(If you know for certain that you've already installed this package you can skip it, though it really won't hurt anything.)
<code> sudo aptitude install libstdc++5 </code>

Now let's make a menu entry for Flock(We like to use our GUI don't we!):
sudo mousepad /usr/share/applications/Flock.desktop

Mousepad will very nicely remind you of the danger associated with editing as root.  Add the following to the file:
[Desktop Entry]
Name=Flock
Exec=flock-browser
Comment=Flock Web Browser
GenericName=Flock Web Browser
Icon=/opt/flock/icons/mozicon128.png
StartupNotify=true
Terminal=false
Type=Application
Categories=Network;Application;


Save your file, and close the sudo enabled Mousepad.  Wait a couple seconds, and check your menu; Flock will be there waiting for you under Applications> Network> Flock. Enjoy!

Just in case you decide you need to uninstall Flock the following undoes what I've done above:
sudo rm /usr/bin/flock-browser
sudo rm /usr/share/applications/Flock.desktop
sudo rm -rf /opt/flock

(XFCE will update the menu for you.)

and removing the archive to save space, (especially if you are indeed uninstalling Flock).
rm ~/Desktop/flock-*.linux-i686.tar.gz

This should work for any distribution, AFAIK, but if it doesn't please let me know and I'll be happy to add and credit your solutions, or help you through getting Flock working on your distribution.  If Flock isn't starting from your menu, and you followed my above instructions, please type <code> flock-browser </code> into a Terminal and let me know what comes out.  Finally, if you use Mac OS X or Windows, there's a Flock for you, too.  Happy blogging!