Mac's Help Viewer is great for when you need a bit of extra documentation, but it annoyingly floats over all your windows so you can't see what you're doing. Here's how to make it act like a normal application.
To make Help Viewer act like a normal window — with its own dock icon and everything — just open a Terminal and type:
defaults write com.apple.helpviewer DevMode -bool true
Hit Enter, and the next time you start it up it should act like a normal application. You can switch it back with:
defaults delete com.apple.helpviewer DevMode
Hit the link to read more. If you're running Leopard instead of Snow Leopard, there's a slightly more involved way to achieve the same result.