This is our text, and it will be a good source to read about things for the details of proofs and for the appendices about basic background
A more concise introduction that also includes some basic material on Riemannian geometry.
A short (less than 150 pages) paperback that is a classic. It covers a lot of introductory material about vector spaces, norms, and so on, but his treatment of differential forms and Stokes' Theorem is more complicated than it needs to be.
A long (5 volumes!) treatise that covers everything we will do in our class and much more. The Volume 1, which can be read alone, covers a lot of what we will do in a very engaging style and in more detail than Calculus on Manifolds.
An even shorter (less than 65 pages) paperback that introduces the all basic ideas of smooth manifolds and smooth maps in a very clear and elegant way. The author doesn't treat a lot of the other topics that we need to treat, but for an introduction to thinking about smooth manifolds, it can't be beat.
From time to time, it will be useful to know that the set of critical values of a smooth map is 'very small'. To be precise, it has measure zero in a precise sense that we will discuss in class. (There's also a proof in Milnor's Topology from the Differentiable Viewpoint, in case you want to look there.)