I second this, helped me a lot, too. In particular, it covers a wide range of topics, each with some introductory exposition, and gives a variety of example questions with answers.

Additionally, glassdoor.com has a lot of user-contributed interview questions and lets you search for/filter by specific companies.

Does it just prepare for code interviews, or do you actually learn something useful with it, besides getting a job?

It is for interviews. You should already know the useful stuff for your job. The best you can do that is relevant to both fronts is

Work through CLRS algorithms book

Practice explaining technical ideas in spoken conversation.