Wi-Fi Sync needs no introduction. Sync your iDevice. Via Wi-Fi. Yeah, that's right, wirelessly.
To get started with Wi-Fi sync you need to download two apps; one for your iDevice and one for your computer. Wi-Fi Sync works with Mac OS X (Snow Leopard, Leopard) and Windows (XP, Vista, 7). You also must be on the same Wi-Fi network on both your iDevice and your computer for this app to work.
Once you have downloaded and installed both apps, simply open the app on your iDevice and accept the pairing. Wi-Fi Sync will now show a message saying your device is ready to sync and it should appear on the devices list in iTunes. Now you can sync exactly like you would if you were using the USB cable.
Obviously, synchronisation will be slower with Wi-Fi Sync than it is over USB, so the first thing I would suggest you to do is disable backups. This can be done from the options in the desktop app. This speeds up the process no end. Also, using Wi-Fi sync will decrease battery life if you are syncing a massive amount of music, apps and video so please remember this before downloading.
There is also a small problem with the desktop app, as there is no option to close it. It doesn't use a lot of memory, so this isn't a massive issue, but I am still amazed that there is no way to close it and ending the process might not even help.
Overall I love Wi-Fi Sync. It does exactly what it's supposed to do and saves you the hassle of plugging and unplugging cables. It's not cheap at $9.99 and your syncs will be slower, but personally I will be using this all the time. Oh, and make sure you show your friends. They'll be impressed, I assure you.
Wi-Fi Sync is available on Cydia for $9.99 and works with the iPhone, the iPod Touch and even the iPad.