In your Highlights area, select the playlist(s) you'd like to send (by clicking in the checkbox to the left of the playlist titles) and click the 'Actions' button along the top menu. Choose the 'email' option:
You can also choose the 'email' option from the actions dropdown box to the far right of a Highlight's title:
Copy the link and paste it into your e-mail message. You can also press the 'clipboard' icon to the right of the link, which will automatically copy the link for you (which you can then paste anywhere you want):