Vegas Hotel Shuttle Buses are a free service. They are meant for anyone that is going to gamble at the destination of that bus so if you are not going where the destination is (like a neighbor casino) just be sure you act like you are going to gamble where the bus is taking you.
Hotel to Hotel shuttles
California to Sam's Town 8:30am-11:30pm runs every 75 minutes
Fremont to Sam's Town 8:15am-11:15pm, runs every 75 minutes
Harrah's to Sam's Town 9:30am-9:30pm runs every 90 minutes
Mandalay Bay Resort to South Point 9:00am-12:30am runs approximately every hour
Palace Station to Tropicana to Fashion Show Mall and back to Palace Station Runs hourly on the hour.
Rio to Caesars Palace 10am-1am runs every 15 minutes
Rio to Bally's 10am-1am runs every 15 minutes
Rio to Harrah's 10am-1am runs every 15 minutes
Riviera to Sam's Town is now only from Harrahs
Sam's Town to California/Fremont 9:00am-10:45pm runs every 90 minutes
Sam's Town to Riviera is now only to Harrahs