When iTunes 7 came out, Apple competely redesigned the iPod section in iTunes. You can now look at all the different kind of files on your iPod using the bar graph at the bottom of the page. This shows the total capacity of the iPod, and how much of that is being used up by Audio, Photos, Videos and Other files. To see this, plug in your iPod and open up iTunes. Click on your iPod in the Devices section in the left hand column.

It gives you the details in terms of the iPods storage capacity, that is, in bytes. However, you can also use the graph to display a count of how many songs, photos and videos your iPod contains or how long it would take to listen to all the songs and watch all the videos.

Change to this mode by clicking on the graph itself. Clicking once will cycle to the number count, clicking again will change it to the time count, and clicking one final time will change it back to the storage capacity.