Essentially what the title says. I need something that will give me a decent introduction into homology theory. I don't need too deep of an understanding, just enough to get through a paper I'm reading.
As has been suggested, the paper I'm reading is On Khovanov's Categorification of the Jones Polynomial, by Dror Bar-Natan, available here: http://arxiv.org/abs/math/0201043
Also I should probably add, I'm a rising sophomore (undergraduate) so I really don't have the background that I should to be reading about homology theory. But my research advisor gave it to me, so I've got to get through this.
As a starting point, the book "Graphs, Surfaces and Homology" (3rd ed.) by Peter Giblin is an outstandingly readable and informative undergraduate introduction to homology. You probably should for now avoid MacLane's "Homology." There is no royal road, remember, and you are entering the gates to someplace where no road is a superhighway.