The Collaborative International Dictionary of English v.0.48:

Assemblage \As*sem"blage\, n. [Cf. F. assemblage. See
   Assemble.]
   1. The act of assembling, or the state of being assembled;
      association.
      [1913 Webster]

            In sweet assemblage every blooming grace. --Fenton.
      [1913 Webster]

   2. A collection of individuals, or of individuals, or of
      particular things; as, a political assemblage; an
      assemblage of ideas.
      [1913 Webster]

   Syn: Company; group; collection; concourse; gathering;
        meeting; convention.

   Usage: Assemblage, Assembly. An assembly consists only of
          persons; an assemblage may be composed of things as
          well as persons, as, an assemblage of incoherent
          objects. Nor is every assemblage of persons an
          assembly; since the latter term denotes a body who
          have met, and are acting, in concert for some common
          end, such as to hear, to deliberate, to unite in
          music, dancing, etc. An assemblage of skaters on a
          lake, or of horse jockeys at a race course, is not an
          assembly, but might be turned into one by collecting
          into a body with a view to discuss and decide as to
          some object of common interest.
          [1913 Webster]

WordNet (r) 3.0 (2006):

assemblage
    n 1: a group of persons together in one place [syn: gathering,
         assemblage]
    2: a system of components assembled together for a particular
       purpose [syn: hookup, assemblage]
    3: the social act of assembling; "they demanded the right of
       assembly" [syn: assembly, assemblage, gathering] [ant:
       disassembly, dismantlement, dismantling]
    4: several things grouped together or considered as a whole
       [syn: collection, aggregation, accumulation,
       assemblage]

Moby Thesaurus II by Grady Ward, 1.0:

122 Moby Thesaurus words for "assemblage":
   A to Z, A to izzard, Bund, Rochdale cooperative, aggregate, all,
   all and sundry, all sorts, alliance, alpha and omega, assembly,
   assembly line, assembly-line production, association, assortment,
   axis, band, be-all, be-all and end-all, beginning and end, bloc,
   body, broad spectrum, building, buildup, coalition, college,
   combination, combine, common market, complement, composition,
   compound, confederacy, confederation, conglomeration, constitution,
   construction, consumer cooperative, cooperative,
   cooperative society, corps, council, credit union, customs union,
   each and every, economic community, embodiment, everything,
   fabrication, fashioning, federation, formation, free trade area,
   gallimaufry, gang, getup, group, grouping, hash, hodgepodge,
   hotchpot, hotchpotch, incorporation, jumble, junction, league,
   length and breadth, machine, magpie, make, makeup, mash, medley,
   melange, mess, mingle-mangle, miscellany, mishmash, mix, mixed bag,
   mixture, mob, odds and ends, olio, olla podrida, omnium-gatherum,
   one and all, organization, package, package deal, partnership,
   pasticcio, pastiche, patchwork, piecing together,
   political machine, potpourri, production line, putting together,
   ring, salad, salmagundi, sauce, scramble, set, setup, shaping,
   society, stew, structure, structuring, syneresis, synthesis,
   the corpus, the ensemble, the entirety, the lot, the whole,
   the whole range, union, what you will