An extremely annoying personal organiser, it is powered by a (usually incompetent) imp, which can perform various tasks. There have been 3 models encountered so far: the Mark 1, mark 2 and Mark 5. All of these start up with an unusually happy tune such as "bingly-bingly beep!", "bingle bingle bingle" or (when wet) "ob oggle sobble obble".
The only known dis-organiser Mark 1 was owned by Samuel Vimes, and was completely incompetent. It claimed to have 15 functions, although it appeared that at least ten were apologizing for the useless manner in which it performed the others. One is the ability to recognize handwriting - "I'd recognize it anywhere" - but not to read handwriting. It is also hinted that one was owned by William de Worde, but it was thrown out of a window for being unhelpful, and was subsequently taken back to the store.
The second version - retail price AM$300 - was also owned by Vimes, and it was also useless despite its ability to inform the user of theoretical future appointments. It was lost in the sands of Klatch, and subsequently started to organise a shark's schedule after being thrown into the sea by Death. Another Mark 2 was also owned by Mr. Pin and Mr. Tulip, but after their death was inherited by de Worde.
An extremely compact model (a "nano imp") was discovered in the Ankhian Embassy in Bonk, where it had clearly been used in the covert assembly of intelligence and useful information about the host nation. While its owner had come a terminal second in the Great Game, the disorganiser had not been found by the werewolves and enabled Vimes to piece together information about what was happening
Also owned by Commander Vimes, the next dis-organiser we encounter is the Mark 5, the Gooseberry, which is much more useful than its predecessors. It has games, such as "Splong", and "Guess my weight in pigs". It has an "iHum" feature, and can also interface with the clacks, enabling Vimes to send messages back to Pseudopolis Yard Watch House. The Gooseberry is also able to read watch reports and do sums. In fact, this model actually works well with Commander Vimes, after a poor start, (such as Vimes telling the Gooseberry to stick its head up a duck's bottom), and has established a case for employment as a Watch member in its own right.
Most Dis-organisers are the product of the Thaumatological Park, a business enterprise set up under the auspices of Unseen University. Utilising what was formerly known as the Unreal Estate, this is now a thriving go-ahead hub of magical business, where the commercial by-products of research magic are made available to the general public. The name of Ponder Stibbons may not be far away from this development, which might explain the extreme honesty of its name.
It is interesting to note that in the trade of Dis-organisers the term "write-only documents" has been crafted.
It is interesting to note how often defective magical devices of this sort end up by being thrown into the sea by their exasperated owner. more here
There is an echo of The Silmarillion here. The last surviving son of the rebellious elf-king Fëanor refuses to surrender the last Silmaril to the custody of the Lords of the West. Under the glamour of its beauty, he argues that the magical jewel is his father's creation and he has a right to it, both as surviving son, and as were-gild for his dead father and six dead brothers. He keeps the stone, despite a curse upon it that makes it leadenly heavy and painful to his touch. Finally he can suffer it near him no more, and throws it into the deepest sea. He then spends the rest of his days wandering the seashore in mingled regret and relief, lamenting what he has lost. This has an odd familiar echo in this context...
(Although if Vimes were ever to take a seaside holiday, his reaction might be "thank the Gods I got rid of the godsdamned thing!" and a nod in the direction of the Sea-Goddess, lest she throw it back...)
There's also a second layer of meaning to Dis-organiser. Not only is it simply the opposite of something that is supposed to help organise your schedule, but Dis is the the name of a city encompassing the sixth through ninth levels of hell in Dante's The Divine Comedy, inspired by a Roman god of the underworld Dis Pater. And imps come from hell. Hence Dis-organiser, a hellish organiser that causes immense frustration to its owner.