Here is a roundup of some of the interesting news released during the later half of July.
JavaScript
Nokia has put together a best practices performance guide. This is especially useful for mobile developers, but the optimizations will improve performance in all browsers. It is very thorough:
http://wiki.forum.nokia.com/index.php/JavaScript_Performance_Best_Practices
Google has released its JavaScript coding guidelines. Most of it is a collection of well-known best practices, but I found the JavaScript Types and JSDoc section to be particularly useful:
http://google-styleguide.googlecode.com/svn/trunk/javascriptguide.xml
Nicholas Zakas explores the various ways to detect if properties exist on objects and reveals the best ways to evaluate property existence:
http://www.nczonline.net/blog/2010/07/27/determining-if-an-object-property-exists/
HTML 5 & CSS 3
David Flanagan has written Canto, a improved HTML Canvas API. While it doesnt add a lot of new functionality, it does make working with Canvas elements a lot simpler:
http://www.davidflanagan.com/2010/07/cantojs-an-impr.html
Mobile
Samsungs relatively new phone, the Wave, comes with a new WebKit based browser, Dolfin. PPK took some time to evaluate it:
http://www.quirksmode.org/blog/archives/2010/07/new_kid_on_the.html
Libraries
Dojo has released version 1.5 with tons of improvements, including better mobile support:
https://www.dojotoolkit.org/reference-guide/releasenotes/1.5.html
YUI has released a preview candidate for version 3.2.0. It includes a lot of nice improvements, but most notably is the mobile support: