I've made many of my product manager interview resources available for free on the web.
There's one item that's coveted more than anything else: my Google Spreadsheet that recommends topics to study and exercises to do for:
- Product design questions
- Metrics questions
- Estimation questions
- Lifetime value questions
- Behavioral interview questions
- Technical questions
- New market entry
- Go-to-market strategy
It also includes links to my two company specific guides: a 30-day study guide for Google PM interviews and a 30-day study guide for Amazon PM interviews. (I do have a 30-day study guide for Facebook PM interviews, in my book The Product Manager interview.)
Best of luck with your PM interviews,
Lewis C. Lin