All problems are from the 2nd edition of the textbook:
Sipser, Michael. Introduction to the Theory of Computation. 2nd ed. Boston, MA: Thomson Course Technology, 2006. ISBN: 0534950973.
Problem Set 1 (PDF)
Problem Set 2 (PDF)
Problem Set 3 (PDF)
Problem Set 4 (PDF)
Problem Set 5 (PDF)
Problem Set 6 (PDF)