Recently added to Highrise's help section:
Question
How do I build a bulk mailing list in Highrise?
Answer
You can do this by giving each contact you want on the mailing list the same tag and then exporting the list.
Here's how: Tag each person you want on the list with a unique tag (for example: "email_list"). There are two ways to do this: 1) Go to each person's contact page and add the tag to that person (click the "Add tags" or "Edit tags" link under the contact's name). 2) Go to the "Contacts" tab and select the checkbox next to any name you want to add to the list. Then click the "add tags" link that shows up at the top of the screen.
Then, click the "Tags" tab and click that specific tag to bring up all contacts on your list. Then click the "Export" link in the sidebar. Choose the format you want and save the list. You can then import this list into the application that you use to send group emails, create mailing labels, etc.