General:
* Seat
* Stool
* Throne (for a very important person)
* Pew (in a church)
* Settee (a longer seat with a back)
* Sofa (a longer seat with a back, more comfortable)
* Diwan (a low, cushioned seat)
For specific uses:
* Work bench: Workstation, table, platform
* Judge's bench: Dais, rostrum
* Park bench: Seat, garden bench, public seating
The best synonym will depend on the specific situation and what you want to emphasize.