Windows only: Microsoft's Windows Live Essentials apps just received a bulk update while in beta, giving Mail much better Gmail folder handling, the underrated Live Writer superior spell checking and Word importing, Photo Gallery some Flickr video, and other improvements all around.
The full list of improvements is posted at the Windows Team blog, but from the looks of things, it's Live Writer and Photo Gallery that got the most attention—although Messenger fans will be happy to know that their chat client is reportedly more efficient with CPU cycles and moves a bit quicker. If you were using Windows Live apps, especially the previous beta release, it seems like a fairly no-risk upgrade.
Windows Live Beta apps are free downloads, and require Windows, as you might expect.
Windows Live Essentials 2011 beta refresh [Windows Team Blog]