Show text using Large Type without relying on third-party applications

If relying on a browser is okay you could do it with large-type.com:

$ open http://large-type.com/#YourText

A slight variation on @iolsmit answer.

Do the same first action. But when you select 'where' to save in the Banner action. Choose other. The Choose folder dialogue will pop up.

Now press down the keys: command + Shift +G

This will slide down will show up.

In its text field; Type or copy & paste:

 ~/Library/Caches/TemporaryItems

Then click GO. This will take you to the Users temporary folder.

Choose it as your selected folder. It will show as 'TemporaryItems'

Now add the action: 'Run Shell Script' in place of 'Open Images in Preview'

The the 'Run Shell Script'; Use its drop down menu for Pass input: as Argument

clear out in text that is already in the large text field. (i.e cat)

And type or paste this in.

/usr/bin/qlmanage -p "$@"

Save you new service. And test

What happens is a new file is saved in your temp folder and the quick looked to display it on the screen. Hit space to dismiss it as normal.