You can fairly easily remove the ugly capitalisation from the sidebar in the new iTunes 7 user interface. Here's what you need to do...
First, make sure iTunes is not running, then control-click on the iTunes application and select Show Package Contents from the pop-up menu. Navigate into Contents -> Resources -> English.lproj (or the proper directory for your locale). In this directory you should see a file called Localizable.strings. Make a backup of this file before doing anything else!
Convert the file to an XML plist in Terminal. Launch Terminal and type this command:
plutil -convert xml1 Localizable.strings -o Localizable.plist
Now open Localizable.plist in your favourite text editor; find and edit the caplitalised strings -- change LIBRARY to Library, for instance. Here's how the lines look in the file:
"135.011" = "LIBRARY";
"135.012" = "DEVICES";
"135.013" = "STORE";
"135.014" = "PLAYLISTS";
When done, save your changes. Then return to Terminal and type:
plutil -convert binary1 Localizable.plist -o Localizable.strings
Open iTunes and you should find that the sidebar no longer has any ugly capitalisation. Note that it is possible to edit Localizable.strings directly with Property List Editor, which is included with the Developer Tools. However, on my G4, editing this file directly was very, very slow.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20060913032817384