If you have a cat who lives outdoors even part-time, here's an article that I found on Purina's Yesterday's News cat litter site that offers some excellent safety advice:
You'll find safety collars, Purina's Yesterday's News paper-based cat litter, and other great products for your cat at petco.com.If your cat is allowed outdoors, train her to wear a safety collar with an expansion device and a tag that gives your cat’s name and your telephone number to distinguish your cat from stray cats. Proper identification enables someone to contact you if your pet wanders far from home. Cats who are allowed to roam may damage neighbors’ gardens or use planters as litter boxes. If you allow your cat outside, keep a watchful eye on her. If she leaves to visit a neighbor, bring her back to her own yard. Keep her vaccinations current and take her to a veterinarian regularly to be certain she is free from internal and external parasites and in general good health.

Pet Emergency Pocket Guide