Windows only: Microsoft just released the beta version of Windows Live Essentials, a suite of free desktop applications including Windows Photo Gallery, Movie Maker, Mail and several more useful apps you may just want to download.
In all, the Windows Live Essentials beta includes an updated Windows Live Messenger for your instant messaging needs, the Mail email client, updated Photo Gallery and Movie Maker, a Sync app that syncs files between Windows and Mac PCs and provides remote access), Writer (the blogging tool) and a couple of other token apps that aren't quite as interesting for most people.
You can download the beta here. If we were you, we'd grab the "Choose the programs you want" installer rather than the default installer (the latter of which defaults to installing the entire suite of programs).
Windows Live Essentials is a free download for Windows only.
Windows Live Essentials beta [Live.com]