Our society, the VvB&BMT (in English: "The Netherlands' Society for Biophysics and Biomedical Engineering") has links to many other groups and societies.
To start with there are really close ties to the Nederlandse Natuurkundige Vereniging (www.nnv.nl). There are for instance membership reduction for persons that are member of both societies. There is also one member of the board of our society (at the moment Tim Markus) member of the editorial board of Nederlands Tijdschrift voor Natuurkunde (www.ntvn.nl), the journal of the NNV. Members of our society can publish papers in that journal also, and are invited to do so, to enhance the visibility of biophysics within the physics community.
Links to other Dutch societies like the Nederlandse Vereniging voor Klinische Fysica (www.nvkf.nl) and the Koninklijk Instituut Van Ingenieurs (www.kiviniria.nl) do exist but are less close at the moment.
Various members of our society are also member of the Koninklijke Nederlandse Academie van Wetenschappen (www.knaw.nl).
The society itself is a member of various transnational organizations. Within Europe these are the European Biophysical Societies' Association (www.ebsa.org) and the European Alliance of Medical and Biological Engineering and Science (www.eambes.org). These organizations play among other things a role in promoting the work of our members at the level of the European Community. Members of our society do play a role in the boards of these European associations/alliances.
We are also a member of the International Federation for Medical and Biological Engineering (www.ifmbe.org) the federation of national societies for biomedical engineering all over the world (to make it slightly more complicated, EAMBES is a member of the IFMBE too).
Together with the International Organization for Medical Physics (www.iomp.org, the NVKF is a member of IOMP) the IFMBE organizes a world congress every three years (2009 was in Munich, 2012 will be in Beijing (www.wc2012.org) and 2015 in Toronto). There are also regional congresses that are organized with support from the IFMBE. For Europe these are the Northern Baltic, the Medicon, and the EMBEC (look at the conference announcements under the conference tab or at the IFMBE website for more information)
The IFMBE and the IOMP also are the two members of the International Union for Physical and Engineering Sciences in Medicine (www.iupesm.org) an umbrella that has as it's major role that it is this union that is a member of the International Council for Science (www.icsu.org). The ICSU is the toplevel union of all worldwide unions of scientific societies.
The IFMBE is an NGO with the World Health Organization (www.who.org). IOMP will probably get that status soon.
Many members of the VvB-BMT are also member of the IEEE EMBS (www.embs.org). That was original a US organization for engineers but is nowadays a world wide organization.
Because we are a member of EBSA and IFMBE, all members have free access to the journals of these organizations, the European Biophysics Journal and the Medical and Biological Engineering & Computing and also some some other publications.