Where to find practical exercises for algorithm analysis? What is a good book or resource to find practical exercises of analysis of the complexity of concrete algorithm implementations (that is, which asymptotic complexity does a particular code have)? 

I'm interested not in solving algorithms but in practising finding out their complexity. I have seen a couple of these kind of exercises in my Discrete Mathematics textbook (Rossen), but I haven't been able to find a good resource to find others.
Textbooks in algorithms are chock full with examples of algorithms, often with analysis. For example, take a look at Erickson's "Algorithms", Dasgupta et al "Algorithms". Looking around for lecture notes will get you a lot of others. Analysis of algorithms requires some specialized techniques, a modern overview is Sedgewick and Flajolet's "Introduction to the analysis of algorithms".