I am puzzled if it is appropriate to ask for resources/referemces for good exercises for an introductory TCS course. I personally think that this is a very precise question, but I see the danger that the answers might depend very much on everyone's personal opinion, which might lead to an open-ended discussion. Also I noticed that related questions such as
Nevertheless, I would really like to know about this. And I can imagine that other users are interested in this as well.
Also, let me know if cs.SE is the right place for this question or should I post it in cstheory.SE. Since I consider the question as non-research-question I would prefer to post it in cs.SE.