The first release candidate for the upcoming WordPress 3.5 is here. This signals that the next release of the popular blogging platform/CMS is almost ready for its big unveiling. Still, it's probably not a good idea to install it on a live website just yet.
While there probably aren't that many bugs left, you don't want to be the one guy in 10,000 to have problems with this testing release.
Still, if you want to check out what's new, you can always set up a test site. And if you're creating WordPress themes or add-ons, it's definitely time to test them with the latest version, which, assuming everything goes smoothly, will be out in a couple of weeks.
The big new features in the latest WordPress are media management tools, better ways to upload files, better ways to insert them in your posts and so on.
WordPress 3.5 RC is available for download here.