The latest, here. I am unaware of any direct link from the Sanders official Senate website, to a Bernie Buzz page; and I believe you get onto a mailing list by that name, from here. Getting the email for some time, I cannot recall how I initiated receiving it. Almost every emailing seems to have a "if you have difficulty reading the email the content is online ..." linkage, but that's only after you are on the list.
I could give the link from the latest email, for the online content, as I did in opening the post.
How to navigate to online archived "Buzz" items is what is presently unclear.
UPDATE: This link, for Buzz archived items:
http://sanders.enews.senate.gov/common/mailings/index.cfm