Gardening and Horticulture - Wood border around garden needed

I need to make my vegtable garden a little smaller, both length and width. I currently am using what the previous owner had in the yard (I think they are rail road ties) to border off the garden. I want to replace the wood - stain it to match the deck, and install it as the new border. However, all the wood I see at Home Depot has been treated to prevent rotting. I would think I don't want chemicals like that in my soil. What's the best wood to use and can I stain it? Also, I need to use chicken wire, I have lots of rabbits and the occasional fox who stops by.

Here's a pic
http://photos.yahoo.com/kevlicko

Hi Kevin

http://eartheasy.com/grow_raised_beds.htm

http://www.raised-garden-beds.com/

These links have some very good info on using a nontoxic wood, where you will have food plants. Arsnic is something I don't want on my land, so I steer clear of the pressure treated lumber.