This is a great question, and we think there are probably quite a few options for you.
We've recently seen bamboo fencing available at Cali Bamboo. Their web site claims that the fencing is "tested and proven in all environments. Cali Bamboo Fences have successfully endured: floods, blizzards, category 3 hurricanes, heat waves, and even baseball bats."
We have no firsthand experience with bamboo fencing, so we're curious if any readers have tried this material.
As a sure-fire solution you could opt for salvaged wood. Try using the directory at the Building Materials Reuse Association to find salvaged materials nearby.
That's all we've got so far -- any other recommendations for Heidi?
Image: Via calibamboo.com