The main mailing list, which everyone should join, is the "BerkeleyTIP Gloabl" list.
This is for discussion about anything & everything.
Go to that page & click the link "Join this group" on the right hand side of the page.
The "BerkeleyTIP" list is for information & discussion about the physical meeting in Berkeley.
The "BerkeleyTIP-Announce" list has about 1 message per month with details about BTIP meetings, etc.