I love documentation. If you work with/are writing code intended for usage and consumption by more than one person, you should love it, too. Documentation and other resources will make or break the success of your project. And the more open and collaborative you want development to be, the more crucial docs become.
With that in mind, here's a list of docs and other developer resources that myself and others find particularly useful, well-written, and otherwise "beautiful". May they serve to inspire you when writing and designing yours.
This should be updated fairly regularly. As usual, pull requests are encouraged.
- Redis Commands - Most of the Redis docs are exceptional, but this section really epitomizes the combination of good design and usability. And all the individual command pages give you the ability to test things out without leaving the page. Pretty close to perfect.
BrightBox Developer Docs - Clean design, easy to navigate, very in-depth.
- Riaknostic - Made possible by Bootstrap, this is a great example of a project homepage that doubles as a documentation teaser.
- GitHub Developer Docs - I don't always get excited about accordion-based navigation, but when I do...
- Dropwizard - Beautiful and concise; another Bootstrap joint. (Coda Hale's Metrics Library uses the same design and is equally as deserving of developer adoration (contributed by mrtazz).)
- Riak Pipe README - The simplicity of READMEs means that you can't obscure shitty content with flashy design. This one is written by my Basho colleague Bryan Fink and should be committed to memory as an excellent example of how to write READMEs.
- Learn You Some Erlang (contributed by @lenary)
- Django Documentation (contributed by @bretthoerner)
- Erldocs.com (contributed by @bradfordw)
- Clojuredocs.org (contributed by @mrb_bk)
- FreeBSD Handbook - Clean and direct documentation of an OS. (contributed by @mrtazz)
- Ruby on Rails Guides (contributed by @seancribbs)
- Pow Annotated Source - Built with docco. (contributed by @BonzoESC)
- Stripe Documentation and Full API Documentation - Multiple languages, example code, good detail on the API; especially love how the API docs show examples for curl and their supported client libraries. (contributed simultaneously by @tnm and @technoweenie)
- Librato Developer Docs - Librato's RESTful API documentation. (contributed by @josephruscio)
- CoffeeScript (contributed by @joedevivo)
- Why's (Poignant) Guide to Ruby (contributed by @joedevivo)
- A Beginner's Guide To HTML and CSS