My go-to resource for practicing is http://leetcode.com. There are a lot of questions ranging from easy to hard and an online judge to check your solution by running test cases. If I remember right, there's also a discussions section. They hit a lot of classic interview questions that help you prepare for those questions that wrap those classic problems in obscurity.

For a refresher on algorithms and data structures, I also like the Harvard CS50 videos up on YouTube. They walk through sorting algorithms and cover the bases of various data structures.