I thought I’d throw together a collection of my favorite half-dozen overlooked iTunes UI features. These range from the fairly unobvious to the very unobvious, so your mileage may vary from mine. Feel free to add your own personal suggestions to the comments.
Move your cursor to either of the history navigation arrows at the top-left of the central iTunes display. Clicking either arrow moves you forward or backward one screen in your iTunes Music Store history. To skip within the history list, press and hold the mouse for a second until the individual history pop-up shown here appears. Select any item to move directly to that page.
iTunes can play back any video that you can watch in QuickTime. DivX or Xvid or other codecs installed for QuickTime work in iTunes. They will not, however, play back on your iPod. To convert a video, Control-click (right-click) a video and select Convert Selection for iPod from the contextual menu that appears. It can take a non-trivial amount of time to convert, for example, a 2-hour AVI movie to an iPod-compatible version.
When you are in the middle of several tasks–for example, updating an iPod, downloading podcasts, playing music, etc.–the small right triangle in the gray circle found in the main status window allows you to switch between each kind of display such as the main scrub bar, the beat box, or download and iPod update progress. The triangle appears only when there’s more than one display to choose from.
Double-clicking on the small icon to the left of any item in the source column opens a new iTunes window with that item (playlist, music store, etc) displayed. The windows float freely and can be individually minimized, closed, etc. You can also drag and drop items between windows, allowing you to select some items from one playlist while looking at another playlist at the same time.
The arrow icons found to the right of track names, artist names and album names automatically search the Music Store for those names. It doesn’t matter whether you purchased the track from the iTMS or not.
iTunes offers many more tags and columns than the default presentation suggests. To add custom columns (such as Track Number, Year, Composer, Bit Rate, Beats Per Minute, etc), Control-click (right-click) on any column header text and select the column you wish to display or hide. Selecting either autosize option will resize column widths in order to display text without cropping.