Following is a list of the largest known objects in our Solar System.  OOSS exhibits include or mention each of these bodies, with the exception of some trans-Neptunian objects.  As the name implies, TNOs have orbits beyond Neptune, and are shown on this list in italics.
  1. The Sun, our star, 1,392,684 km in diameter.
  2. Jupiter, a planet, 139,822 km in diameter.
  3. Saturn, a planet, 116,464 km in diameter.
  4. Uranus, a planet, 50,724 km in diameter.
  5. Neptune, a planet, 49,244 km in diameter.
  6. Earth, our planet, 12,742 km in diameter.
  7. Venus, a planet, 12,104 km in diameter.
  8. Mars, a planet, 6779 km in diameter.
  9. Ganymede, a moon of Jupiter, 5268 km in diameter.
  10. Titan, a moon of Saturn, 5152 km in diameter.
  11. Mercury, a planet, 4879 km in diameter.
  12. Callisto, a moon of Jupiter, 4821 km in diameter.
  13. Io, a moon of Jupiter, 3643 km in diameter.
  14. The Moon, Earth’s only natural satellite, 3474 km in diameter.
  15. Europa, a moon of Jupiter, 3122 km in diameter.
  16. Triton, a moon of Neptune, 2707 km in diameter.
  17. Pluto, a TNO and dwarf planet, 2372 km in diameter.
  18. Eris, a TNO and dwarf planet, 2326 km in diameter.
  19. Titania, a moon of Uranus, 1577 km in diameter.
  20. Haumea, a TNO and dwarf planet, probably highly ellipsoidal, long axis 2000 km (est).
  21. Rhea, a moon of Saturn, 1528 km in diameter.
  22. Oberon, a moon of Uranus, 1523 km in diameter.
  23. Iapetus, a moon of Saturn, 1469 km in diameter.
  24. Makemake, a TNO and dwarf planet, 1430 km in diameter (est).
  25. Gonggong, a TNO and possible dwarf planet, 1230 km in diameter (est).
  26. Charon, a moon of Pluto, 1207 km in diameter.
  27. Umbriel, a moon of Uranus, 1169 km in diameter.
  28. Ariel, a moon of Uranus, 1158 km in diameter.
  29. Dione, a moon of Saturn, 1123 km in diameter.
  30. Quaoar, a TNO and probable dwarf planet, 1121 km in diameter (est).
  31. Tethys, a moon of Saturn, 1062 km in diameter.
  32. Sedna, a TNO and probable dwarf planet, 1000 km in diameter (est).
  33. Ceres, a dwarf planet in the main asteroid belt, 946 km in diameter.

If this list were extended in order to include the largest 100 objects in the solar system, the remainder of the list would be comprised almost entirely of TNOs.  However, a handful of these largest additional objects are found inside the orbit of Neptune:
  • Vesta, a main belt asteroid, 525 km in diameter.
  • Pallas, a main belt asteroid, 512 km in diameter.
  • Enceladus, a moon of Saturn, 504 km in diameter.
  • Miranda, a moon of Uranus, 472 km in diameter.
  • Hygiea, a main belt asteroid, 430 km in diameter.
  • Proteus, a moon of Neptune, 420 km in diameter.
  • Mimas, a moon of Saturn, 396 km in diameter.
These objects are roughly half the size of Ceres, so even at the scale of this solar system diagram, they are practically microscopic.  However, their orbits are shown in OOSS exhibits because Mimas is the smallest known planetary-mass object, meaning it has enough gravity to pull itself into a rounded (or ellipsoidal) shape.
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More info: List of solar system objects by size (Wikipedia)