Windows/Mac OS X: Free remote desktop application CrossLoop has just released a Mac version, which means simple, cross-platform remote support and file sharing for your friends and family.
The benefit of CrossLoop has always been that it's very easy to set up and use, even for beginners, making it an ideal tool for those of us who've been unofficially designated as tech support for our loved ones. Just install (on both your computer and the computer you want to control), sign up for accounts, and you'll be up and sharing screens in no time once you swap the automatically generated access code. I don't see any new options (screen sharing and file sharing have always been CrossLoop's bread and butter), but the addition of Mac support should open a lot of new doors for helping out across platforms. CrossLoop is a free download, Windows and Mac only.