As part of Google's Caja project, they have released a JSON library (for JavaScript) that looks like it's very solid. For more information on the Caja project, check out this Ajaxian article.
A user reported to me a strange behavior with IE6 and Flash that I've never noticed. If you're using IE6 and there's a SWF on the page when you go to another Application Window and came back to IE6, if the cursor was placed in any text box, the focus will be lost.
The quickest way to verify this bug is to go to the Adobe website and place your cursor in the "Search" box at the top of the page. Now ALT+TAB to another Window. Now ALT+TAB back to IE6. You'll notice the cursor is no longer in the search box.
Now, if you do the same test on the Google website you'll notice this behavior doesn't exist.