This variety of beer is made throughout the low countries and Germany, particularly Bavaria. I believe you will also find the brewers of Northern France making them! Wheat beer has come a long way since the mid-1970s when it almost died out in Germany: nowadays most German bars have a Wheat beer on alongside a lagered beer, especially in Bavaria.
This style is known by different names depending on country and language. The most common names are Weisse, Wit, Witbier, Biere Blanche and Tarwebier: these basically all translate as either White or Wheat beer.
Wheat beers, as the name implies, are made using all, or partial brew of Wheat. (In Germany, the standard proportions are 50% wheat and 50% barley.) If it is unmalted, the wheat can leave a stronger grainy flavour, like freshly baked bread.
These beers are usually top fermented and are brewed to around 5%. The German varieties tend to be darker and spicier, whereas the Dutch and Belgian versions are lighter and more citric.
Weisse beers are best served chilled and can be very refreshing, particularly on a hot day. Germans often also add a slice of lemon.
All bottled wheat beers are drunk with yeast (German Heffe) in. The sediment should be swirled in the bottom of the bottle and added after most of the beer has been poured into the glass. There are such oddities as "Crystal Weisse", which has had the yeast sediment removed, but to me this spoils the beer - and of course, you cannot do the "swirl".
These beers are also sweeter than other types. The one exception are the Berlin Weisse beers, which are rather sour, and usually have fruit syrups added to them. If you can, try Berliner Weisse without fruit syrup - it's very interesting!
The best known White beer is Hoegaarden, which is on sale quite widely in the UK. As long as it continues to be produced in Belgium, it will probably remain a reasonable beer. If it starts getting brewed in this country, my advice would be to avoid it. It is real in the keg, even though it is served using gas to push the beer to the pump. If you see it, then try it; however it is usually rather expensive.
If you really want good weisse beers, then look around. There are others on the market and most of the big supermarkets produce their own version, based mainly on German Weisse beers, and most are quite drinkable, if a little bland.
For pure refreshment, I prefer a Dutch wheat beer, as these are usually the most citric. For more interesting tastes, the Germans usually have the edge. Try a dark German wheat beer for a real treat!
I have included some notes on a couple of my favourite weisse beers. As always, see what you think.
Leeuw Valkenburg Wit: This is one of my personal favourites and comes from a small regional brewery in Valkenburg near Maastricht, very close to the Dutch/German border. The beer is 4.8%, soft, sweet and citric with a hint of spice.
Schneider Weisse: This is probably about the best German Weisse bier I have come across. It was available through a well-known supermarket a couple of years ago, but I haven't seen it recently. The beer itself is quite dark, but a lovely creamy mouthfeel, slightly sour with spices!