Cookies and persistent logging in for web applications:

HTTP Cookies
LoginGenerator for Ruby on Rails
Best practices for Login Cookies
Rails persistent login
TaskTHIS an application with persistent logins. Excellent resource, download the source, it's got a lot of good stuff in it.

AJAX:
AJAX - Don't believe the hype. Brothers and sisters.

Music Annotation:

Music Annotator
Annotator

CSS Dynamic Style:
Dynamic Drive CSS Style Libraries

Ruby performance:
Performance testing with Ruby blocks

bzr - A new kind of version control system. Looks very cool.
bzr installation
SFTP for bzr - paramiko - SSH2 protocol for python
bzr plugin registry