Thought I would add this one to the list. It is more of a journal than some of the others listed. I did a quick search and did not see that it had been posted about in the forums before.
For Linux, Windows (install or portable), even says Mac.http://rednotebook.sourceforge.net/index.html
RedNotebook is a modern journal
It includes a calendar navigation, customizable templates, export functionality and word clouds. You can also format, tag and search your entries. RedNotebook is Free Software under the GPL.
* Spell Check
* Format your text bold, italic or underlined
* Insert Images, files and links to websites
* Links and mail addresses are recognized automatically
* Automatic saving
* Backup to zip archive
* Word Clouds with most often used words and tags
* Export the journal to PDF, HTML, Latex or plain text
* The data is stored in plain text files, no database is needed
* Translated into more than 20 languages
There are a number of review links at the bottom of the screenshots page. One person wrote his comparison with Evernote. One thing I like about it is it isn't "cloud" based. Though he says you could via one of the 3rd party online storage sites.