<p>Is anyone out there using D for real world applications? If so, what are you using it for? I can't seem to find anything big on the web written in D.</p>

<p>Despite the lack of known big users, D seems like a very promissing language to me, and according to <a href="http://www.tiobe.com/index.php/content/paperinfo/tpci/index.html" rel="noreferrer">TIOBE</a>, it's fairly popular.</p>

I suppose we can read something into the lack of immediate answers to this question and that is that not many/any of the acive stackoverflow responders are using D. I was also a little surprised about the level of its ranking in the TIOBE listing that you link to.
Having said that, Walter Bright has been working on the language for quite a number of years now and I think he has quite a number of `followers' who remember what a good job he did with the Zortech C++ compiler back in the '90s. I also note that the language appears to be leaning towards the functional direction now.