I saw some recently at KMart. Just two sets so far though, the Cat Woman chase with Batman and the Lex Luther one with Superman and Wonder Woman. I also saw the technic build for batman, green lantern, and the Joker.
The Lego company has stopped making Lego batman but you can still buy them at amazon. As of 2012, Lego also started a DC Superheroes and Super-villains theme. The link can be found below. You'll find some Batman sets ;)
eBay, Amazon or the Lego website are the best places to buy Lego train sets.
Yes, they have made contracts with DC Comics and Marvel to make sets of various superheros such as Wolverine and Iron Man.
There are about 55 Lego Harry Potter sets to buy.
eBay
The best place to buy old Lego sets are from the Internet. Sites like eBay or Amazon are among the cheapest, most reliable sites to buy Lego. I'm sure you'll find lots of Lego Spiderman sets there!
toysrus
Lego marvel superheroes get released on March 2012 in Australia.
Yes, Lego Superhero sets are available to buy in Legoland.
Yes... looks like LEGO Superheroes will be coming out soon. I saw a superman LEGO guy on the LEGO site recently... not to buy yet, but should be soon.
walmart
Dc superheroes