In today's electronic age it is easy to forget the basic courtesies of applying for a job. Emailed applications should be treated no differently to postal applications and the importance of some form of covering letter should never be underestimated.
The cover letter can be described as the trailer to the main feature and its main function is to get your CV read. It is a chance to make personal contact and provide a link between yourself and the position for which you are applying.
The following checklist should help: