Why is Home Sharing not working with iPhone? I have a Mac Mini with iTunes 10.2.1 installed, I enabled home sharing in the preferences and the Advanced menu. I also have an iPhone 4 on iOS 4.3, which I enabled home sharing on using the same username and password that my desktop uses.

Both computers are connected to the same home network. When I open up the iPhone's iPod app, however, I don't see any of the songs that are only on the Mac. I only see those that have been synced with the iPhone (i.e. I use this Mac to sync my iPhone).
Launch the iPod App on your iPhone. At the bottom of the screen, you should see a More button with 3 blue dots.

As you can see here, there is a Shared list item at the bottom of the page. Click that, which should bring you to a screen like:

 

Click the name of the computer that you see in your list and then all of the videos, movies, tv shows, etc, will appear in your lists for those items.

In other words, the iPod App won't keep the home-shared content separate. You will see the Home Sharing content as if it was integrated with the device.