Technology on Majipoor is quite a mixture, with some remnants of the high level of a spacefaring culture (mostly very old). For most inhabitants, beasts of burden rather than powered vehicles are the norm. Research is rare — the only example I can think of is the development of the King of Dreams equipment. Very few understand the old technology well enough to repair devices that break down.
The Lady and the King
Both the Lady of the Isle of Sleep and the King of Dreams have devices that allow them to enter or influence the dreams of people all around the planet. It would appear that the Barjazids developed the King's dream machinery independently of any detailed knowledge of the Lady's equipment.
There are a number of wheelless vehicles, mainly in government use, referred to as floaters. They seem to involve some sort of antigravity technology rather than being forced-air hovercraft.
Weather control is mentioned in regards to the vicinity of Castle Mount, though details are sparse. A breathable atmosphere seems to be maintained up to a much higher elevation than would be naturally possible.
Genetic engineering
Throughout the course of the stories, numerous musical instruments are named, among them the galistane and the sistiron.
Soul-painting