Ask HN: What projects should be on every developer's "bucket list?"

By this I mean what project should everyone build not because its useful or new, but because the process of building it forces you to learn something new. Some examples I've heard are your own programming language or a simple implementation of a database.

Text editor, compiler, BASIC interpreter, virtual machine emulator, CRUD application, web server, Lisp interpreter, Forth Interpreter, SQL database application.

Repeat the above as gui applications, and on the web.

I think writing a book about something technical. Either self-published (I like leanpub) or through a publisher. Doesn't have to be long, even a 30 page ebook is a big effort.

I have done this a few times and you learn so much and appreciate so much.

Other than that, I think it really depends on where you are starting. If you are a webdev, building an MVC framework. If you are a system programmer, building a basic HTTP.1/1 web server.

A raytracer and an emacs mode.

An ERP and a blog engine with the first post being about it