YayText is a tool for for creating bold, italic, strikethrough, cursive script, bubble text, tiny text, and more using unicode characters. Text made with this tool can be pasted into Facebook and Twitter posts, etc.
Replace plain text with Styled text
Textlicious is a tiny extension 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.