One of the new features Apple has added to OS X in the most recent version is a dictation service, where you can speak phrases and paragraphs and have the system input them into any supported text field.
Being a global service, Dictation is available in most browsers, word processors, and other programs where you might input a considerable amount of text.
When enabled in the Mountain Lion "Dictation & Speech" system preferences, then when in a text field you simply need to press the Function key twice, and the small dictation indicator will appear. Spoken phrases will then be sent to Apple where they are processed and sent back as text.
While relatively straightforward, there may be some frustrations when using the Dictation service, especially when it comes to inputting punctuation, symbols, and properly capitalizing components of words.
Unfortunately the dictation service cannot interpret every nuance of your voice and determine the proper punctuation from it, so as with any dictation, you need to be exact in your descriptions of where the punctuation is.
For example, if you want Dictation to type "I once saw a man (a VERY LARGE man), who was climbing a tree." You would need to explicitly say the following phrase:
"I once saw a man open parentheses a caps on very large caps off man close parentheses comma who was climbing a tree period"
These in-line commands include many other details such as new line, new paragraph, various other punctuation marks and symbols, and are necessary for proper structure of your paragraphs. However, while you can try figuring these out for yourself, doing so may be a bit difficult. Therefore, if you use the service you may find Apple's outline of its supported Dictation commands to be a useful resource. In that article, Apple lists all commands that will work with its service, along with some additional tips to make the best of Dictation.
In addition, while you might find yourself attempting to talk normally to the dictation service, if you slow down a touch, enunciate words clearly, and use the proper in-line commands, then dictation can be quite efficient and relatively error-free. With a small amount of practice, the Dictation service can be a valuable augmentation to a number of text-processing routines in OS X.