NixNote, formerly Nevernote, is an open source client for Evernote . It is written in Java so it will also run on Windows & OS-X, but the primary focus has been to try and get a usable environment for Linux.
Rebel aims to provide you a distraction-free note taking experience. Focus more on writing and less on formatting and saving. As you write your note, Rebel will format it based on your markdown syntax.
Write beautifully. Organize easily. Find everything. Fuss free writing. Saves notes as RTF files on user specified folder. Can search across all notes. No sign up/log in required. Portable application.
Geeknote is an opensource Evernote console client for Linux, FreeBSD and Mac OS X. Use it for system administration needs, creating notes, notebooks, sync your local directories with Evernote notebooks.
Passfindr is a web based premium Personal knowledge base, Password manager and Bookmark manager application to securely store passwords and other sensitive information in a virtual vault locked with individual master passwords.