Sossusvlei is a common tourist destination in the southern part of the Namib Desert, Namibia. The word vlei is an Afrikaans word that means "marsh" and Sossusvlei is in a small valley between the dunes which sometimes gets snow! The name of the 'town' (i.e. petrol station) is Sesriem, also the name of a nearby canyon.
Deserts, though they are very harsh, are a delicate ecosystem with a surprising amount of life living around and underneath the dunes. Keep this in mind when roaming around and driving in the area.
The Namib Desert is the oldest desert in the world and stretches over 1,500 km from the Orange River in the south into Angola in the north. There is a wide range of landscapes in the Namib, from gravel, to rocky mountains to huge dunes in varying colours of sand.
Sossusvlei is a salt and clay pan created by the Tsauchab river that flows through the Sesriem Canyon every 5 to 10 years. Even in very wet years it does not reach the Atlantic Ocean but drains away between the dunes of Sossusvlei.  Sossus means "place of no return" (note: there are other explanations, this is the one given by local guides).
The mud from the river stacks up at Sossusvlei and after some 1000 years the river searches its way through the next row of dunes. This is how the place called Dead Vlei was created, here the river used to drain away many years ago. Because of the lack of water all the trees in this valley have died, so the meaning of "Dead Vlei" becomes clear.
What makes the sight of the Dead Vlei so remarkable is that there is not even moisture enough for normal decomposition to occur. So all the trees here, though dead, have been nearly perfectly preserved for centuries.
Sossusvlei/Sesriem are the better part of a day's drive from Windhoek. There are some rather difficult mountain passes on some secondary roads, so you'll have to choose your route wisely if you don't bring a high-clearance vehicle (there are several routes from Windhoek). The best route without nasty mountain passes would be from the south-central town of Mariental. On the other hand, the passes provide excellent viewpoints.
Sossusvlei is inside Namib-Naukluft National Park so a permit is required to enter. Permits can be purchased at the park office just inside the gate at Sesriem. The gate opens at sunrise and closes at sunset.
The road from the accommodations in Sesriem to Sossusvlei itself is 65 km and tarred for all but the last 5 km. The last 5 km are through soft sand so you will need an all-wheel-drive to drive it. Alternatively, you can park your car at the end of the tarred road and either walk the last 5 km or take one of the shuttles that regularly run between the end of the tarred road and Sossusvlei (for a fee). You can also walk one way and take a shuttle the other.
Transport and guided tours to and from Sossusvlei are also provided by some of the lodges for their guests.
The only place to get food, other than at fancy resort restaurants, is from the small general store at the Sesriem petrol station.
There is a bar at the Sesriem campground where most people hang out after a hard day of hiking in the desert.
There are a number of luxury resorts in the surrounding area, as well as a government-run campground with good facilities which is very close to Sossusvlei.
Don't get lost while wandering in the desert. And remember to drink plenty of water (as you should be doing throughout your time in Namibia, as it is a very dry country).