Body of email along the lines of "Dear Mr X, please find attached my Letter of Application and Resume for xx position. Kind regards GeminiSix" with the letter and resume attached as 2 separate word documents.
This is what I'd do. Where I work the applications are printed out to be shortlisted and presented to the interview panel. It looks nicer when the cover letter is printed from a properly formatted attachment rather than presented as a printed e-mail. While the content is the important thing of course, it never hurts to take an opportunity to demonstrate that you care about the way that documents are presented (especially if basic computer skills are required for the job).