Compagnie des Autobus de Monaco operates a bus line that threads the avenues of Monaco. Purchase your ticket on board for €2; or save 50 cents a ticket by buying in advance from an agent, a machine, or online. They also operate a solar electric boat from Quai des États-Unis to the casino (there's an elevator at Parking du Pécheurs); it runs daily from 8 to 8 (€2).
The Conseil Général has an express bus that connects Place des Moulins in Monaco with Vauban station in Nice (past the Palais des Expostions); tickets for the 100X (express bus) cost €4, but run only Monday to Friday. The Lignes d'Azur 100 bus costs €1.50 and leaves from the Ségurane stop at Place Garibaldi in Nice—but be prepared for a long ride, as it takes about two hours. A very popular mode of transport to the Principality, the 100 is often full, so it's best to take it directly from Nice or Monaco; otherwise it will drive right by you, no matter how frantically you wave. Info for both can be found on the same website.
Compagnie des Autobus de Monaco (377/97–70–22–22. www.cam.mc.)
Lignes d'Azur (04–93–85–64–44. www.lignesdazur.com.)