Q:

Where do I learn the basics of cohomology?

I am fishing for a textbook on basic Algebraic Topology. Almost every where I looked, I saw praises for Hatcher's textbook. Now, I already know a little bit of Homology (at the level of Munkres' Elements of Algebraic Topology), but looking at Hatcher's chapter on Homology I realized that I wouldn't have been able to learn much from it. For a lack of a better phrase, it would have appeared too hand-wavy for someone like me (due to my lack of mathematical maturity).
So, my question is where (apart from Munkres, preferably online) do I turn to learn the basics of Cohomology (say, at the level of Hatcher's chapter 3)? 
PS: And, since I am a poor student, online lecture notes would be great.
Added
Thanks everyone. But, I should have stressed that I am looking for lecture notes or textbooks that are freely available online. So I'll wait a bit more before accepting.
@Theo Buehler: Massey looks great. Thanks a lot. Unfortunately, I do not have access to my univ library over the summer. But, if I don't find any notes etc. then I'll accept your answer if you post it. 

A:

Firstly, I think that Munkres is excellent. But I also agree that Hatcher's is less accessible than Munkres. In addition to the excellent comments above (Theo's recommendation of Massey, even though expensive, is great - and if you are a student with access to a math library, I bet it will be there).
But I point you to the Autodidact's Guide, something published in Notices of the AMS a while back. It recommends different books for almost every subject, and their topology section is right on.

A:

I haven't seen it as my library doesn't have it (yet), but there are very good reviews for Tammo tom Dieck's book
It presents the proof of a number of results that were previously unknown to be possible without spectral sequences.
Google link

