I could've sworn that Download.com got rid of their Mac software section a while ago, but alas: digg submissions never lie. CNET's Download.com has posted a list of top iTunes add-ons for tackling everything from grabbing album art to watching who is listening to which songs from your library. Included in the list is RadioLover which lets you record streaming radio, as well as iPodRip with (thankfully) an accurate explanation as to why its abilities aren't included in iTunes itself. This list actually part of a guide Download.com wrote called iTunes Advanced, which includes some handy tips for things like adding an equalizer column to your list of songs to easily assign custom EQ settings to specific songs, as well as a list of hotkeys for the default iTunes visualization mode.
Seasoned iTunes pros will probably balk at getting iTunes advice from Download.com, but there are probably at least a couple handy tidbits here for just about everyone.