Chrome: Google Chrome has a built-in speech recognition system, but you can only use it in certain places. Dictation is a webapp that uses Chrome's speech recognition engine, but allows you to dictate much larger chunks of text.
From the Dictation webapp, you can either click the microphone, or hit Ctrl+Shift+. (full stop) to activate dictation mode. When speaking, Dictation recognises "new line" to create a new paragraph, and "delete everything" to start over. Once your text is dictated, you can hop right in and correct any mistakes within the app's editor. When you're done you can copy and paste the text into your favourite text editor. If you've ever wanted to play around with the idea of dictation, but didn't want to spend money on specialised software, Dictation is a free alternative that works well.