Here are my solutions to various problems in the textbook Quantum Field Theory for the Gifted Amateur, by Tom Lancaster and Stephen J. Blundell (Oxford University Press, 2014). Obviously I can't offer any guarantee that all the solutions are actually correct, but I've given them my best shot.
These solutions are the only ones that I've worked out so far, so please don't ask me to post "the rest of the chapters" as I haven't worked on those yet. I will get to them eventually.
Chapter 1 - Lagrangians
1.1, 1.2, 1.3, 1.4, 1.5, 1.6
Chapter 2 - Simple harmonic oscillators
2.1, 2.2, 2.3, 2.4
Chapter 3 - Occupation number representation
3.1, 3.2, 3.3, 3.4
Chapter 4 - Making second quantization work