Notepin is described as 'offers a dead simple way to create public notebooks for free, with no registration required. And for a small premium, you can upgrade to password protect your notes' and is an website in the Office & Productivity category. There are more than 50 alternatives to Notepin, not only websites but also apps for a variety of platforms, including Windows, Android, iPhone and Mac. The best alternative is Joplin, which is both free and Open Source. Other great sites and apps similar to Notepin are Google Keep (Free), Evernote (Freemium), Simplenote (Free, Open Source) and CherryTree (Free, Open Source).
Joplin is a free, open source note taking and to-do application, which can handle a large number of notes organised into notebooks. The notes are searchable, can be copied, tagged and modified either from the applications directly or from your own text editor.
Telegra.ph is an anonymous publishing platform by Telegram that lets anyone post stories without having to register an account. Simply visit the site and you'll be presented with a light form for posting.