This is survey of membership/participation policies adopted by various other IMCs. The opinions represented here belong to whichever IMC is cited, not STLIMC.
First off don't forget the national Indymedia volunteer page:
http://volunteer.indymedia.org/
chicago.indymedia.org
Folks curious are asked to simply contact the IMC by email/phone, or attend meetings to "to learn more and to get more involved." The various public and non-public elists are enumerated below. They also explain that the "the content of our meetings is dictated by the participation and interest of its members." Editorial collective membership is also explicitly stated as open to the public.
http://chicago.indymedia.org/mod/info/display/about/index.php
indybay.org (Bay Area)
Must first join a working group by attending meeting and joining e-lists. Then, to join collective, must...
1. Attend a new volunteer orientation.
2. Agree to our Principles of Unity.
3. Agree to our Rights & Responsibilities document.
4. Send an email asking to join to sfbay@lists.indymedia.org. You will be contacted by a membership clerk, who will attempt to assist you through a three month probation period. During this period, you will be expected to perform as a full member, regularly attending general and/or working group meetings. Upon completion of the three months, your membership clerk will recommend you for membership to the collective.
http://www.indybay.org/newsitems/2003/12/15/16659011.php
nyc.indymedia.org
"The general NYC IMC collective meets for general meetings every month .... These are inter-working group meetings designed to address the administration and maintenance of the NYC IMC. Anyone interested in participating in, or learning more about the IMC is encouraged to attend media production team meetings before coming to a General Meeting."
http://nyc.indymedia.org/en/static/about.html
ucimc.org (Urbana-Champaign)
"The UCIMC is organized into Working Groups which each have responsibility for different areas of the Center's operations. A good way to get involved is to attend a meeting for the Working Group that most interests you. All group meetings are open to the public and all groups are eager to accept new members! You can also sign up to be on any of the Working Groups' e-mail list .... You may attend the IMC's semi-monthly Steering Group or semi-annual General Membership meetings to get a sense of the overall workings of the IMC."
http://www.ucimc.org/info/volunteer
There are also plenty of steering groups.
http://www.ucimc.org/info/volunteer#steer
Membership requires financial donation (sliding scale)
http://www.ucimc.org/info/membership
portland.indymedia.org
"Structure is not derived from a centralized bureaucratic process, but from the self-organization of autonomous working groups that recognize the importance in developing a unified approach. These groups can be centered around a set of tasks (e.g., web design, tech, editorial), a type of media (e.g., video, print, web radio), an activity (e.g., promotion/outreach, reporting), or some other project. portland indymedia working groups can organize themselves in whatever fashion they find most appropriate to their needs (e.g., frequency of meetings, method of communication, open or closed listserves, etc.) as long as they stick to the portland indymedia principles of unity. ... Meetings occur regularly to foster cooperation among individuals and working groups, and are open to people who are interested in supporting portland indymedia projects or starting new ones."
http://portland.indymedia.org/en/static/about.shtml
Interested folks are asked to email imc-portland-requests@lists.indy with relevant subject heading (i.e. volunteer, video, audio).
http://portland.indymedia.org/en/static/volunteer.shtml
dc.indymedia.org
"The DC Independent Media Center has organized itself into a media cooperative, meaning that people who participate in DC Indymedia get access to all of the cooperative’s resources while also agreeing to help sustain and grow the cooperative. The most simplistic explanation is that of a food cooperative. When people participate in a food cooperative they get access to what the organization offers but also agree to contribute time and/or a donation to keep the cooperative going. We understand that there will be many public users at the DC-IMC space, such as people who are just passing through town or dropping by periodically to check out the space. The DC-IMC cooperative welcomes public users. However, when somebody begins using the space and resources on a consistent basis, they will be asked to join the cooperative.
Participants of the DC-IMC do their work either through a working group or through individual or autonomous projects. An example of a working group is the editorial working group, which works on the DC-IMC website. For individual or autonomous projects, individuals freely associate and collaborate to produce the media that is important to them. However, because all participants use resources of the DC-IMC cooperative, we ask you to sign the Cooperative Agreement below. In exchange, you get access to the resources of the DC-IMC."
http://dc.indymedia.org/mod/info/display/co-op/index.php