Textlicious

Textlicious is a tiny service that lets you enter styled text in places that normally accept only plain text. Make your tweets more expressive, your texts stand out, and your posts on the ‘book the envy of all your friends. Just highlight any text you’re typing in any app, right-click, and select the style you want from the Services pop-up menu. Available styles include bold, italic, serifed, typewriter, script, double-struck, and more.