As with any legally binding contract, it's best to check with a lawyer. The ASMP Stock Photography Handbook includes an Adult Release, Minor Release, Simplified Adult Release, Pocket Release, and Property Release - all available online at NPPA's Business Practices Committee Web Site. In addition, Susan McArtney has a book titled Travel Photography: a Complete Guide to How to Shoot and Sell that includes copies of simple model releases in 33 different languages that can be copied and used. (Seed, 1996)
See The PDN Guide to Model and Property Releases for more information.