One of the things we had to do after having our daughter was to child-proof a number of things around our house. Ensuring that bookcases (and similar furniture) didn't tip over was of primary concern, so I looked for various options. After trying some strap-style tie-downs (which didn't work worth a darn), I found the Hangman Anti-Tip Kit, which is marketed partially towards anchoring furniture in earthquake-prone areas. This device is simple to install, and is as solid as a rock. Highly recommended for those in a similar situation.