Last.Fm Records shows cd covers for cds your listened to, according to last.fm. It can show covers in a page or post, and you can add it as a widget.
4a. (widget) If you want to show the cd covers in your sidebar, go to the widgets settings and enable the widget. Here you can add a title for the widget.
4b. (shortcode) this plugin now has its own shortcode:
[lastfmrecords]. It uses the global plugin settings, but comes with arguments to overrule them. More info on the arguments under