sudo sh -c "echo 'deb http://ppa.launchpad.net/inkscape-nightly/ppa/ubuntu jaunty main' >> /etc/apt/sources.list"
Replace jaunty intrepid, if you use Ubuntu Intrepid Ibex.
Ubuntu Karmic Koala users, just use the following command:
sudo add-apt-repository ppa:inkscape-nightly
2. Add the GPG key:
sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys EC6B3CAD
3. Install Inkscape
sudo apt-get update && sudo apt-get install inkscape-devel
This does not uninstall any installed version of Inkscape, as it installs a development version.
If you wish to uninstall any older version of Inkscape:
sudo apt-get remove inkscape
Please note: this version of Inkscape does not create a menu entry, so to run it, press Alt + F2 and enter:
inkscape-devel
Alternatively, you can right click one of your panels or desktop and select "Create New Launcher" and in the command field, enter "inkscape-devel".
Update: actually, it does create a menu entry under Applications > Graphics, I don't know how I missed it... :)
Later Update: the final version of Inkscape 0.47 is out. Read HERE how to install it.