The most common means are:

Human power (rowing, paddling, setting pole etc.)
wind power (sailing)
Motor powered screws
Inboard
Internal Combustion (gasoline, diesel)
Steam (Coal, fuel oil)
Nuclear (for LARGE boats)
Inboard/Outboard
Gasoline
Diesel
Outboard
Gasoline
Electric
Paddle Wheel
Water Jet (Jet ski, Personal water craft, Jetboat)
Air Fans (Hovercraft, Air boat)