Here is a list of all time top posts from this blog. Currently there is only one but be sure I will be adding more to this.
Here is a list of 10 puzzles which have been asked on a Google Interview. They are not in any specific order.
10 Microsoft Interview Questions
Here is a list of 10 puzzles which have been asked on a Microsoft Interview. They are not in any specific order.
If you're looking for some serious preparation for your interviews, I'd recommend this book written by a lead Google interviewer. It has 189 programming questions and solutions:

Very good Collection of Questions.
Nice collection 🙂