Answer by Andrew Maiman:
In the current version (2.0.7) of VLC for Mac, the option for scrobbling has been moved into the ‘Advanced’ preferences panel. To access it, select ‘VLC -> Preferences’ and then click the ‘Show All’ button in the bottom-left corner. Next, select ‘Interface -> Control Interfaces -> Audioscrobbler’ and enter your Last.fm username and password. Leave the ‘Scrobbler URL’ as the default of post.audioscrobbler.com.
Next, select ‘Control Interfaces’ and check the ‘Submission of played songs to last.fm’ checkbox.
Click ‘Save’ and then quit and re-launch VLC. Your played tracks will now be scrobbled to Last.fm. Note that it does not submit the track until is has completely finished playing (unlike other scrobbler apps that will send it after 50% of the playback.)