Step by step:
- Download HamachiX, and have your friend do the same.
- Run HamachiX and let it do all the fun things it needs to do. Then click the Plus button and make up a network name and password. Optionally open the Preferences and set a nickname for simplicity's sake.
- Choose Create Network [and have your friend launch HamachiX and choose Join Network].
- Give HamachiX a minute, and hit Refresh until you see your friend is connected.
- Open iTunes and set up Home Sharing with the same account on both machines. If you had previously set up Home Sharing, click Advanced » Turn Off Home Sharing, then turn it back on to switch usernames.
The initial period where iTunes finds the other machine took a while. At first only one library showed up, and then eventually both did. We just kept restarting iTunes and Hamachix until things worked. We also turned on file sharing and were able to access each other's computers, but I'm not sure if that is necessary for the iTunes Home Sharing.
[robg adds: This hint is usable for a completely legitimate reason: You can use it to share your home iTunes library with your own laptop while traveling. As for sharing your library with a friend, the legality of that depends on the files you're sharing, and the laws of your country. Mac OS X Hints isn't responsible for how you use this hint, so proceed at your own risk. Also note that this means you'll need to share your iTunes account info, which (to me, anyway) means you're unlikely to use this to share with just anyone.]

