We have started to do a lot of work with JQuery to simplify the development process. For those that have not come across JQuery before, it is " a fast and concise JavaScript Library that simplifies HTML document traversing, event handling, animating, and Ajax interactions for rapid web development. jQuery is designed to change the way that you write JavaScript ". The ability to select multiple items on a page with a single line of script is great. For deployment, the library is simply a single .js file that needs to be put onto the server and referenced on a page.
Aside from the core JQuery library, there are hundreds of plugins (additional script files) such as JQuery UI.
As a starting point, look at Jan Tielens article.
One of the exciting things for me about using this technology is the ability to use on hosted, or shared SharePoint servers (where as a developer you cannot add .dll files, features or solutions). To implement jQuery on a page in this scenario, we could upoad the library (jquery-1.3.2.js) into a document library, add a Content Editor Webpart onto a page then edit the webpart to reference the file and start using it. Imagine, with a Content Editor Web Part and a few script libraries, we could implement a tabbed style webpart, loading data from our lists :)
I'm planning on putting a short series of JQuery articles and links here over the coming weeks