Unobtrusive Javascript:

Some topics covered in the video:

A bit of history and how we got here.
Semantic Markup
Obtrusive Examples <– big belly here
Benefits of coding unobtrusively
Examples, specifically to Rails
Guidelines and assumptions you should make when coding javascript
Graceful degredation
Namespacing

[Via: Rails Envy]

JavaScript Libraries By Comparison [5]:

There are several factors to consider when compiling the necessary information for this comparison. The first, and most important, is terminology. Even though there are numerous features and functionalities for each JavaScript library that are similar, they do not always fit neatly into predetermined headings. It remains imperative that each library feature be weighted while keeping this in mind, and when appropriate, read the full description that accompanies each heading. This is a fantastic starting point for your own research and analysis.

[via: javascript ant - Articles]

Aaron Newton popped a nice link in the comments too about why he chose Mootools. Definitely worth a read if Mootools is on your radar.