The best place I have found to get bottles is at recycle bins. I have collected about 10 cases in 3 weeks. The nice thing about these places is that the bottles are separated by glass color and since people have stored them they usually rinse them out. You can also get the boxes the bottles came in so you can store them neatly. You do have to go through the bottles to weed out the twist off bottles. I have so many now, I have started separating them by type (i.e. Standard, New Belgium, Sam Adams, etc) so when I bottle my beer, I do not have to label them to keep up with what style of beer is in the case. I do keep records on bottling dates!
Good Luck in your search!