Nevernote, an open source Evernote clone for Linux now has an Ubuntu PPA you can use to stay up to date with the latest releases.
The Nevernote PPA provides stable packages and is available for Ubuntu Lucid, Precise, Quantal, Raring and Saucy. Add the PPA and install Nevernote using the commands below:
sudo add-apt-repository ppa:vincent-c/nevernote sudo apt-get update sudo apt-get install nevernote
Once installed, launch Nevernote from Applications > Internet.
Update: Nevernote is now called NixNote.
Thanks to tolizban for the tip!