I'm going to visit family in Canada in a few weeks and I cannot find my passport. Do we still need our passports to get back in the U.S. or is our green card and drivers license enough id?

I know there was a new Law passed that said, you need US passport to enter Canada, or Mexico, but I'm not sure if this law has took affective yet. If it hasn't, you can use your Green card. Otherwise, get a copy of your passport.

I think if you are traveling by air you'll need a passport to get on the plane, if you're going by ground, the green card should suffice.

Yes, Reba is correct. If you are traveling by air, you will need your passport. If you are driving, you will need proof of your Canadian citizenship for the Canadian border (birth certificate should be fine) and your green card for the return to the US. The passport requirement for land borders is currently slated to go into effect for June, 2009 although that date can change. Have a good trip.