What documents do I need when traveling to Canada?

I'm planning a trip to visit some friends in Windsor, Ontario and I was planning on driving through the Detroit-Windsor tunnel to get there. I've been told that all I need to get in is a Valid Photo ID like a driver's license and a Birth Certificate. I can do that but I've also been told that I need a passport which I can't acquire in time. Do I really need the passport?

No, you don't need a passport. A valid gov't issued photo id and birth certificate are all that is required. (presuming you're an American). Effective June 2009 you'll need to have a passport. You might be interested to know that the passport requirement is not/will not be to get into Canada, it will be to get into the USA. Come June 2009, every person will need a passport to enter the USA, including American citizens.

you do not need a passport until June 2009
what you have is fine

I live in Windsor and cross that border all the time. What the others have said is right; at present (assuming you are a U.S. citizen) all that's required is valid government-issued photo ID (i.e. your driver's licence) and your original birth certificate for any land crossing (flying is different and requires a passport). The passport stipulation for land crossing has been delayed until at the earliest June, 2009.