Pure CSS solution:
Use the :first-line pseudo-class.
display:block;
Width:40-100px; /* just enough for one word, depends on font size */
Overflow:visible; /* so longer words don't get clipped.*/
float:left; /* so it will flow with the paragraph. */
position:relative; /* for typeset adjustments. */
Didn't test that. Pretty sure it will work fine for you tho. I've applied block rules to pseudo-classes before. You might be stuck with a fixed width for every first word, so text-align:center; and give it a nice background or something to deal with the negative space.
Hope that works for you. :)
-Motekye