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Memos - Easily capture and share your great thoughts. Open Source and Free forever
(www.usememos.com)
Hosting your own services. Preferably at home and on low-power or shared hardware.
Also check out:
I liked it when I tested it but just like Silverbullet (another interesting self hosted note taking app) there is no offline mode/offline storage. I keep my home server only available locally, so I need notes stored e.g. on my phone as well and cannot rely on connection to my server.