WordNet (r) 3.0 (2006):

speak up
    v 1: express one's opinion openly and without fear or
         hesitation; "John spoke up at the meeting" [syn: opine,
         speak up, speak out, animadvert, sound off]
    2: speak louder; raise one's voice; "The audience asked the
       lecturer to please speak up"

Moby Thesaurus II by Grady Ward, 1.0:

66 Moby Thesaurus words for "speak up":
   affirm, affront, allege, announce, annunciate, appear, argue,
   assert, assever, asseverate, aver, avouch, avow, beard,
   bell the cat, bite the bullet, brave, brazen, brazen out,
   break silence, come forth, confront, contend, declare, enunciate,
   express, face, face the music, face up, face up to, front, have,
   have no secrets, hold, insist, issue a manifesto, lay down,
   maintain, manifesto, materialize, meet, meet boldly, meet head-on,
   open up, pipe up, predicate, proclaim, profess, pronounce, protest,
   put, put it, run the gauntlet, say, say out, set at defiance,
   set down, speak, speak out, stand for, stand on, stand up to,
   state, submit, take a stand, take the floor