Inevitably in design you will have to fill body copy to show a client what a design will look like. As a standard we have always used Lorem Ipsum for this. For anyone unaware, Lorem Ipsum is the dummy text that has been the industry standard since the sixteenth century. It is preferrable to use Lorem Ipsum to keep the reader from being distracted by content in the layout, and it is more-or-less the same character distribution as English copy. Here are a few sites where you can find Lorem Ipsum, or similiar copy with some humor injected:
If you find yourself in need of showing the placement of copy, but for some reason don't want to distract your client with words (in english or otherwise) you might find this site helpful:
Just like with text, there are a variety of sites online that offer services to generate placeholder images. A few that I have found most useful are: