Initial Drop Cap is a plugin that will make the first letter of a post, or page, a drop cap. Drop caps are a typographical element where the first letter of a text, or paragraph, is different, usually bigger and sometimes beautified with illustrations.
Although the effect should be done by CSS, inconsistencies and idiosyncrasies in themes make that somewhat difficult to do. The difference between browser in what they accept in CSS is also somewhat of a problem.
The plugin by default shows drop caps on single post pages and single pages, that can extended o the home page, the front page, and archive pages. The styles can be completely tweaked to your specific needs.
You can download the plugin here.
Installation, in your Admin page, choose Plugin -> Add Plugin. Then choose Upload Plugin, upload the downloaded zip file, activate, and done