WordNet (r) 3.0 (2006):

band together
    v 1: form a group or unite; "The groups banded together" [syn:
         band together, confederate]

Moby Thesaurus II by Grady Ward, 1.0:

100 Moby Thesaurus words for "band together":
   accompany, act in concert, act together, affiliate, ally,
   amalgamate, associate, associate with, assort with, attend, band,
   be in cahoots, be in league, bunch, bunch up, cabal,
   cement a union, centralize, club, club together, coact, coalesce,
   collaborate, collude, combine, come together, companion, concert,
   concord, concur, confederate, consociate, consolidate,
   consort with, conspire, cooperate, couple, couple with,
   do business with, federalize, federate, flock together, fuse, gang,
   gang up, get heads together, get together, go along with,
   go in partners, go in partnership, go partners, go with,
   hang around with, hang together, harmonize, herd together,
   hold together, hook up, hook up with, join, join forces,
   join fortunes with, join in, join together, join up with,
   join with, keep company with, keep together, league,
   league together, make common cause, marry, merge, organize, pair,
   pair off, partner, play ball, pull together, put heads together,
   reciprocate, run with, stand together, stand up with, team up,
   team up with, team with, throw in together, throw in with, tie in,
   tie in with, tie up, tie up with, unionize, unite, unite efforts,
   unite with, wait on, wed, work together