A raised platform in a room for a high table, a seat of honour, a throne, or other dignified occupancy, such as ancestral statues; a similar platform supporting a lectern, pulpit, etc., which may be used to speak from.
The canopy over an altar, etc.
A bench, a settle, a pew.
Any physical or media platform which gives prominence to the person on it and the views they espouse.
A talk about one's pet topic (or the topic itself), especially when only tangentially relevant to an ongoing discussion.
A soapbox car.
A crate for packing soap.
To give a speech from (or as if from) a soapbox.