Applications for Homology The Question: Are there any ways that "applied" mathematicians can use Homology theory?  Have you seen any good applications of it to the "real world" either directly or indirectly?
Why do I care?  Topology has appealed to me since beginning it in undergrad where my university was more into pure math.  I'm currently in a program where the mathematics program is geared towards more applied mathematics and I am constantly asked, "Yeah, that's cool, but what can you use it for in the real world?"  I'd like to have some kind of a stock answer for this.
Full Disclosure. I am a first year graduate student and have worked through most of Hatcher, though I am not by any means an expert at any topic in the book.  This is also my first post on here, so if I've done something wrong just tell me and I'll try to fix it.

There are definite real world applications. I would look at the website/work of Gunnar Carlsson (http://comptop.stanford.edu/) and Robert Ghrist (http://www.math.upenn.edu/~ghrist/). Both are excellent mathematicians. 
The following could be completely wrong: Carlsson is one of the main proponents of Persistent Homology which is about looking at what homology can tell you about large data sets, clouds, as well as applications of category theory to computer science. Ghrist works on stuff like sensor networks. I don't understand any of the math behind these things.
Also there are some preprints by Phillipe Gaucher you might want to check out. Peter Bubenik at cleveland state might also have some fun stuff on his website.
