Our team has successfully submitted 140 correct solutions to acm, of which i myself contributed 100+ ones. =)
By working on these acm problems, i learned some new algos/techniques while being more familiar with some old algo/DS.
Effort should be continued in the next month and hopefully submit more acms.
P.S. The book Introduction to Algorithms is such an invaluable resource that you simply cannot avoid reading it. Here is an online version of this book (But i highly recommend that you buy the hardcopy. Bet you will never regret for it). Along with the book, here are MIT videos of algo lessons. Enjoy.