You may already be familiar with the 'Street Surfer' or 'Wave' that gained popularity in 2010 for its radical design and snowboard like feel. This is 'Razor's' version. A cheaper alternative but still loads of fun.
The board works on two wheels, instead of a 4 like a traditional skateboard. Each wheel is set on a rotating caster which is angled towards the rear of the board. The board is split into two foot pads, these are connected by a strong spring in a rotating axle. With this configuration it is possible to propel the board forwards by snaking it from side to side. so that rear wheel follows the front in a wave pattern.
At first it may seem utterly confusing, I suggest learning with someone who can support you while you get your balance. It is in fact quite easy to pick up, and once you have your balance you can start to exploit this board's unique feature.
The twisting axle means that this board can be 'edged' into turns. Imagine a snowboard as it turns and slides the rear out, or imagine an oversteering rally car. The feeling of carving down a big hill is very similar to that of snowboarding or surfing.
This idea was first seen in the higher quality 'wave' by streetsurfer for around £90
At half the price this razor copy is a very good deal. It uses standard skate bearings and roller blade wheels so you can get spares once you wear them out. Construction is pretty good. It can take a beating as you fall off. The top surface can be a little slippy and benefits from adding more skate grip tape
Unlike skateboarding it is extremely difficult to ollie (jump) the ripstick or perform flip tricks. Some people do but be prepared to fall off alot if that's your aim.
For this money, you have to give waveboarding a go. Its a blast carving round town, but best used on downhill runs where you need not keep putting speed in.