Three collaborative spaces I know well enough to recommend, written up in response to a friend’s search.
Open floorplan collectivist space, with lots of community facilities including a full kitchen and side rooms with whiteboards and phones. Some have reported eerie quiet in the main area during the day weirds them out but you should try it and see for yourself.
They host an all-day open house once monthly.
A mix of open plan and “fireboxes” which are little cubes (what a bad name right?). Less techie, more traditional professional services vibe. Their “5 day a month” membership level includes access to conference rooms. Also in a cool neighborhood, which is nice for thinking/walks.
A Portland institution and that has helped filled the void (along with CoAg) left when Cube Space closed in 2009.