Whether seeking space for group sessions, workshops, meetings, brainstorms or events here are a few resources that have interesting/creative spaces.
With spaces in San Francisco, Boston, New York, Montreal and Ottawa, Breather has reasonably priced spaces available the same day at an hourly rate: https://breather.com
With spaces in San Francisco, Los Angeles, New York and Seattle, Peerspace is another great option: https://www.peerspace.com