For the glass-is-half-full optimists at Trash for Teaching, an empty plastic water bottle doesn't have to be tossed into the blue recycling bin. Instead, it can be turned into a vase -- and a lesson in repurposing. The Los Angeles-based nonprofit collects castoff materials from manufacturing operations for use in local school arts and crafts programs. It found that standard water bottles fit neatly inside cardboard spools discarded from fabric knitting mills. The vases are thoughtful hostess gifts. They're $10 each at Zero Minus Plus at Fred Segal in Santa Monica, (310) 395-5718, www.zerominusplus.com, and can also be purchased at Trash for Teaching's online store, www.trashforteaching.org.