You can get a couple of free extensions for Firefox which will generate Lorem Ipsum text for mockups. I prefer the extension called "Dummy Lipsum." Very easy to install and the dummy text it generates can be cut and pasted in any application. Find it here.
Of course, for strictly TYPO3 work, you can also install the Lorem Ipsum TYPO3 extension. I often will install this for the initial development of a TYPO3 site but then disable it once the site starts getting live content.