Meet up with Montana Linux people on IRC. We currently gather at the #ubuntu-montana room on the freenode network. Stop in and say "hello" or even ask/answer some questions. Don't have to be a Ubuntu user either.
See also the MontanaLinux.org calendar provided by Zimbra in both iCalendar and http formats.
BillingsLUG
The BillingsLUG meets every 3rd Thursday of the month at 7PM: