[ilian]

Another open source Evernote/Onenote alternative is TagSpaces(tagspaces.org) It runs completely offline on Windows, Linux, Mac OSX and Android, and since recently it features a server edition, running on top of a ownCloud installation.

[krupan]

Tagspaces is nice. Works the same on Linux, Mac, and Android (probably Windows and iOS too, I haven't tried). I like that it doesn't try to tackle note taking and synchronization. You can use dropbox/spideroak/btsync/owncloud/whatever-you-lik for that.