Matt Schwartz: Based on his very popular introductory QFT courses, Matt's book is excellent in its balance between concentration of useful things and accessibility. It beautifully discusses connections of QFT with classical electromagnetic theory i.e. black hole radiation, and with non-relativistic quantum mechanics (and e.g. its perturbation theory), among other things. It is a very pragmatic guide not only for a phenomenologist, telling people what works – I sort of like it because I have learned from similar books a lot when I was a teenager. There are many problems in each chapter and their usefulness have been tested by Harvard graduate students. The main goal is a practically oriented one: to help the reader become a skillful practic in the Standard Model and perhaps theories extending it. A shorter free web version.
Peskin and Schroeder. This textbook has become the new mainstream standard and replaced many older books such as Bjorken-Drell.
Weinberg's three volumes. Steven Weinberg who needs no introduction wrote a more detailed set of three volumes with some interesting yet reliable things that go well beyond the mainstream material. The three volumes are Foundations, Modern Applications, and Supersymmetry.
Mark Srednicki. The textbook of the physicist who is also the chair of physics at UCSB has been available online and it has been praised by many readers. It's time for you to buy the real version.
Anthony Zee. Anthony Zee is Mark Srednicki's colleague from UCSB. His book is really cute, has a funny cover, and offers some intuitive physical concepts that are not explained elsewhere, much like some cute stories from the history of physics.
Tom Banks (2008). I recommend you a new book on quantum field theory by my (former) adviser, Tom Banks. There's a lot of wisdom – especially some conceptual wisdom – that I have learned from, too. For example, at the very beginning, he starts with a wonderful explanation why "fields" are needed to combine relativity with quantum mechanics at all – why there would be conflicts with locality (signals can't propagate superluminally) if you worked with a wave function for 1 particle (or another fixed number of particles) only. Many things are presented in a similar way as I would do, and others are done differently. A nice summary of LSZ formalism, gauge invariance and its roles, the fate of different types of symmetries, phases of gauge theories, renormalization and the logic of effective field theory, instantons, and monopoles, among other things.
Álvarez-Gaumé and Vázquez-Mozo. An invitation to QFT. You may get a similar text freely on the arXiv.
Lowell Brown. Lowell Brown's book has been praised because of its pedagogical value but be ready that its scope is limited. The author chooses a perspective in which quantum field theory is just another level of computing mechanics and quantum mechanics. That's why things like non-Abelian gauge theories are completely missing.
Renormalization methods: a guide for beginners, by W.D. McComb. It is a fun book that can explain renormalization even to undergraduates, as many reviewers argued. Renormalization is normally associated with quantum field theory - and the text covers some of it - but it first appeared in classical physics. Many examples are very intuitive and accessible.
Michio Kaku: Quantum field theory, a modern introduction. Covers quite a lot, from motivation, Noether theorems, type of scattering, gauge theories etc. to BRST quantization (only two pages), string theory, supersymmetry, and quantum gravity. Sometimes the presentation may be too short but it is helpful as reference and there are other advantages. Includes extensive problem sets.
Eberhard Zeidler. I haven't read it but among other things, this book has a very detailed coverage of history, the role of Göttingen, a presentation of heuristic methods etc. Quite original!
This list is far from complete but if someone is looking for a textbook, it could be useful. See a similar list of string theory textbooks and the 2012 explosion of stringy/SUGRA/QFT textbooks, including one new QFT textbook that looks really cleverly organized and balanced.
Many of the readers have strong opinions - and they may want to share their ideas what they think is most important for teaching QFT. In what direction would you push the classes? What do you think is missing in the mainstream courses and/or textbooks?