This is a great set of best practices for Javascript. #4 nicely sums up the direction I see Javascript taking (XHTML + CSS + JS include = application).
bobbyvandersluis.com | Ten good practices for writing JavaScript in 2005
4. Create easy applicable JavaScript
Unobtrusive scripting bridges the gap between ‘designers’ and ‘coders’. There is a big group of people in today’s industry that does know how to write (X)HTML and CSS but doesn’t feel very comfortable with the DOM and JavaScript. Unobtrusive behavior introduced a mechanism to easily apply small portable scripts to a Web page: “Just make sure your markup looks like A, include this script B, and as a result you have a page that can do C”.
Try to create small pieces of independent code. The disadvantages of a lot of existing JavaScript code libraries are that you often have to include a lot more code than you really need and that they are harder to understand and maintain if you didn’t create them yourself. Because the functions in these libraries are often grouped and reused by other scripts, it often feels like they are spaghetti-coded. A library with small unobtrusive scripts has the advantage of being light-weight, easy to be understood and easy to be adjusted for more specific implementations.