Body wrap filter is a small theme-helper module which provides an input filter to wrap the contents of the node's body field in a div.
Sometimes, when I'm working with custom content types that may have many additional fields besides the title and body content, it can be tricky to style the content that was added to the body field. It can be done using a theme template (.tpl.php) and writing each field separately, but this can be tedious when a simple div wrapper around the body field would suffice.