If you are a programmer, this blog post has a good list of the 10 questions that every programmer should ask during an interview. You can read the post as to why each question matters and what sort of answer you should be looking for, but for the lazy here is the list of questions:

1) How many hours are in a typical work week?
2) What are the expectations regarding travel?
3) On average, how long does an employee remain with your company?
4) What kind of on-going training can I expect to receive?
5) Can you give me an overview of the development process?
6) Who is your largest client, and what can you tell me about the work you do for them?
7) Can you discuss any growing pains experienced by the company in the last two years?
8) How is a typical performance review handled?
9) What types of social activities are organized throughout the year?
10) Can you tell me if I have the experience you need?