Algorithms: Design and Analysis Parts 1 and 2 (https://www.coursera.org/course/algo and https://www.coursera.org/course/algo2) taught by Tim Roughgarden of Stanford. Tim's the best professor I've ever had either on or offline and he does a fantastic job explaining the concepts and breaking down the algorithms into digestible, intuitive pieces. His enthusiasm for the topic and the impressive algorithms is contagious and keeps the challenging courses fun and interesting.
Functional Programming Principles in Scala (https://www.coursera.org/course/progfun) by Martin Odersky, the inventor of Scala, is also excellent and a great way to learn and start using Scala and functional programming. Be forewarned though, once you get a taste of Scala, you'll have to be dragged kicking and screaming back to using Java :-).
Also, Algorithms, Part I and II (https://www.coursera.org/course/algs4partI and https://www.coursera.org/course/algs4partII) by Kevin Wayne and Robert Sedgewick of Princeton University. They approach algorithms from a slightly different angle than Stanford course does and in my opinion they complement each other very well. I was very impressed by the lectures, practical problems, the autograder, and the 'Algorythms 4th edition' book.
p.s. don't expect any certificate of acomplishment for those courses though. I did them both close to 100% and they did not even show up in completed courses on Coursera. I guess it's the Princenton thing, and I came just for the knowledge so that was fine with me.
Functional Programming Principles in Scala (https://www.coursera.org/course/progfun) by Martin Odersky, the inventor of Scala, is also excellent and a great way to learn and start using Scala and functional programming. Be forewarned though, once you get a taste of Scala, you'll have to be dragged kicking and screaming back to using Java :-).