Linesetter helps you reformat your paragraphs.

If you start out with ugly long lines of text, or unsightly short ones with a ragged right edge, linesetter will whip your text back into shape by putting as many words on each line that will fit in 78 characters, while retaining a left-side indent of spaces.

We the People of the United States
in Order to form a more perfect Union, establish Justice, insure domestic Tranquility,
provide for the common defence, promote the general
Welfare

We the People of the United States in Order to form a more perfect Union,
establish Justice, insure domestic Tranquility, provide for the common
defence, promote the general Welfare

Simple, easy, effective.

gem install linesetter

You can drag the Linesetter.tmCommand file from extras/ into TextMate's Bundle Editor to get a handy command that runs linesetter from TextMate. It's set up with a default keyboard shortcut of ⌘+ (⌘⇧=).