Where to place JavaScript in an HTML file?

The Yahoo! Exceptional Performance team recommend placing scripts at the bottom of your page because of the way browsers download components.

Of course Levi's comment "just before you need it and no sooner" is really the correct answer, i.e. "it depends".

The best place for it is just before you need it and no sooner.

Also, depending on your users' physical location, using a service like Amazon's S3 service may help users download it from a server physically closer to them than your server.

Is your js script a commonly used lib like jQuery or prototype? If so, there are a number of companies, like Google and Yahoo, that have tools to provide these files for you on a distributed network.