Desert of Desolation is probably the BEST Forgotten Realms adventure ever to be made, together with Ruins of Zhentil Keep, Curse of the Azure Bonds, and Ruins of Myth Drannor! It refers to the Raurin desert, near Mulhorand the land of the Pharaohs, and a quest to retrieve a set of artifacts, which have been scattered across the vast desert and lie hidden inside pyramids (tombs), protected by powerful and very evil denizens.
Ranging from background history, to city and social descriptions, to important people and characters (NPC's), to adventure hooks and encounter tables, to magical items and artifacts, to the respective gods and monsters, this module has it all and more.
It is a quest of epic proportions, a campaign really, so a lot of time is needed to go from beginning to end (expect your characters to rise several levels by the time it's over). Nevertheless, one can easily run many of the adventures separately so as to make single sessions out of it.
As a result, I have had endless hours of gaming enjoyment playing on material presented within the pages of the Desert of Desolation module!
For other FR references/adventures, I recommend: the Old Empires accessory on Chessenta, Mulhorand, and Unther, the Dreams of Red Wizards accessory on Thay, the Pirates of the Fallen Stars, Moonsea, Dwarves Deep, and Draconimicon accessories (they are Second Edition AD&D, out of print and it will take a bit of searching, but it's well worth it).
Also recommended, the Third Edition Forgotten Realms Campaign Setting, which even though is quite expensive, is still very useful to all FR fans!
In short, if you have love dungeon crawling, pyramids, mummies, and a good challenge, try and get your hands on a copy of Desert of Desolation. It's GREAT! You will not regret it!