Notestack.me is described as 'web-based Simplenote client for the modern browser. It takes advantage of browser localStorage, a new HTML5 feature, to store your notes locally and make them available even when your internet connection is down'. There are more than 50 alternatives to Notestack.me, not only websites but also apps for a variety of platforms, including Windows, Android, Mac and iPhone. The best alternative is Joplin. It's not free, so if you're looking for a free alternative, you could try Standard Notes or Evernote. Other great sites and apps similar to Notestack.me are Simplenote (Free, Open Source), CherryTree (Free, Open Source), Zoho Notebook (Free Personal) and Trilium Notes (Free, Open Source).
Bananote is a fast loading, no nonsense, easy to use note taking app. Quickly add notes in just a few taps. Edit or delete unwanted notes with just a swipe. Lock your private notes with a password or mark important items with an indicator.
Publicnote is a super-simple, free, public notepad. Enter any title to access a note. No account required. Every note is public. You are free to modify any note you find. Every note is encrypted. You must know the title to see the note.