iTunes is a free application for Mac and PC. It plays all your digital music and video. It syncs content to your iPod, iPhone, and Apple TV. And it's an entertainment superstore that stays open 24/7.
Windows 32-bit - Download
Windows 64-bit - Download
Kies allows you to effortlessly sync your contacts, calendar, content, and much more besides. It's a one stop desktop app that intelligently allows you to stay in control of your content at all times.
Kies for Windows - Download
Kies3 for Windows (Android OS 4.3 and over) - Download
Kies for Mac - Download
If iTunes is failing to download an iOS update, try manually downing the iOS files here
iPhone 3GS - iOS 6.1.3 - Download
iPhone 4 - iOS 7.1 - Download
iPhone 4S - iOS 7.1 - Download