This Modular Snake Robot from Carnegie Mellon University has some amazing moves. Take a look at this video showing their snake robot and its many unique gaits.
(Modular Snake Robot gait video)
Just in case you missed some, here's a robotic snake gait summary:
Sine waves are sent through the length of the snake robot, propelling it either forwards or backwards. This gait is particularly suited for fitting into tight areas.
Sidewinding was inspired by sidewinding biological snakes, and is currently one of the fastest ways for these snake robots to travel. This gait is ideal on rugged or uneven terrain.
The snake curves slightly into a 'C' shape and then rolls sideways. It is useful for uneven terrain and excels at climbing hills.
Since the robot is buoyant, sending sine waves backwards through the body of the robot propels it forward.
Channel climbing is a variant of linear progression, where the amplitude and period of the sine wave are adjusted to fit the chosen channel or pipe; protective skin or rubber can provide additional friction and compliance.
Similar to channel climbing, the snake can also climb up the inside of pipes or tubes. A variant of linear progression can be used to climb a pipe or tube, as in a channel, but since a pipe is cylindrically symetrical, the snakes can also use a modified version of corkscrewing to climb a pipe. Since corkscrewing up a pipe uses all 16 servos, as opposed to just 8 as in linear progression, corkscrew climbing is faster.
Pole climbing refers to moving upwards on clylinders whose perimeter is less than the length of the snake robot. The robot moves upwards without the aid of any adhesive by spiraling its body around the pole, gripping it, and using the rolling gait to travel up or down the pole.
Cornering is a motion to maneuver around tight corners, such as those encountered in pipe systems or at the intersection of ibeams.
Pipe rolling moves the snake robot efficiently & reliably across the top of a pipe. The snake robot wraps its head and tail around the pipe and uses the rolling motion to move forward.
As far as I know, the earliest mention of the idea of a snake-like robot is the mining worm robot from Emmett McDowell's 1946 short story Love Among The Robots.