How many times have I wanted to delete a song in playlist and got annoyed about having to go to the library to find it? Lots! Now I've learned that I don't have too.

iTunes has a keyboard shortcut that lets you delete any song from your library, even if you're inside another playlist. Just hold down the Option key while you hit the Delete key (Option-Delete) for any song in any playlist. When you do so, iTunes will delete the song from your entire library.