Churches

• Presbyters (ministers of the Word and Sacrament also called pastors) - Responsible for teaching, preaching, baptisms, pastoral care, leadership, management, ...
• Elders - Generally responsible for internal affairs. They make up the Session of the Church which is responsible for governing the church.
• Deacons - Generally responsible for external affairs. They represent the caring (welfare) side of the church and seek to minister either within or beyond the community of faith. They also dispense the sacraments.
  In the Catholic Church deacons may preach, teach, baptize, witness marriages and conduct funeral liturgies.

Ministries are organizations within the church such as Sunday School (children/youth), adult education, womens group, mens group, music, outdoor, ...
  Women's groups are sometimes called "circles".
  Small groups may meet weekly or semi-weekly.
Activities include things like bible study, book discussion groups, outings, softball/basketball teams, ...

Support groups may include things like Grief sharing, divorce recovery, Substance abuse, ...

Missions support Local, Regional, National and International projects, either monetarily or with time and talents e.g.
Local - Clothing and food drives, soup kitchens, homeless shelters, inner city church support.
Regional - Home repair, Habitat for Humanity
International - Schools, hospitals, orphanages, Missionaries.

Committees (Teams) may include, Nominating, Hospitality, Personnel, Finance, Stewardship, ...

Another Org chart

National - International

Pope, who is the Bishop of Rome
 The Holy Father is advised by his College of Cardinals (who are always Bishops).
 The Curia, divided into dicasteries (congregations, tribunals, offices,
 secretariat of state, etc.), is the agency through which the Vatican is governed.
  Province - A group of dioceses usually within a state or part of a state in the U.S.
     The lead Bishop in a province is their archbishop
     and his diocese is the archdiocese
  Dioceses - There are 2,795  each overseen by a Bishop.
      There are about 200  Dioceses in the U.S.
      The chief church of a diocese, or "the Bishop's church," is called a "cathedral"
    Parish - Staffed with one or more Priests
      There are about 22,000 churches in the U.S. with 70 million members.
      See USCCB - (Office of Media Relations) - Catholic Information Project
    Average attendance was 850.
    Some bishops are also given the honorary title of Cardinal.
    These are usually conferred upon bishops of influential or significant dioceses
     or upon bishops who have distinguished themselves in a particular area of service.
     There were 18 American cardinals in 2008.

See: Parishes, Dioceses, Archdioceses, Patriarchates
Web Site Info For Roman Catholic Dioceses and Parishes within the United States

Protestant:
There are about 100 million protestants in the U.S.
The largest denominations are Baptist (35 M), Methodist (14 M), Lutheran (9 M), Church of Jesus Christ of Latter-day Saints (Mormans) ( 6 M) Presbyterian (4 M).
The median congregation size in American protestant churches is about 160
according to the National Congregations Study at Duke.
The median number that regularly participate is 75.

Number of persons associated with a congregation

Size	Frequency	Percent	Cumulative Percent
5 to 49	200	13.4	13.4
50 to 99	307	20.6	34
100 to 249	491	32.9	66.9
250 to 499	261	17.5	84.4
500 to 999	119	8	92.4
1,000 to 2,499	72	4.8	97.2
2,500 to 4,999	24	1.6	98.8
5,000 to 9,999	14	1	99.7
10,000 or more	4	0.3	100

Number of adults that regularly participate in the congregation

Number	FrequencyPercent	Cumulative Percent
5 to 49	687	45.6	45.6
50 to 99	380	25.2	70.9
100 to 249	283	18.8	89.6
250 to 499	89	5.9	95.6
500 to 999	41	2.7	98.3
1,000 to 2,499	22	1.5	99.7
2,500 to 4,999	4	0.2	100
5,000 to 9,999	1	0	100
10,000 or more	0	0	100

Source: 2007 Data at Duke's National Congregations Study

More statistics at Religion Stats and Christian Denominations

Presbyterian:
The Presbyterian theory of government developed in Geneva under John Calvin and was introduced to Scotland by John Knox.
The Presbyterian Church in the USA has gone thru many iteration with denominations splitting off and later rejoining. The largest ones in 2010 were PC USA (80%), PC America (13%) and The Evangelical PC (3%). Most are organized as follows (some skip the synod).

General Assembly - Ruling Body
  Synod - There are 16
    Presbytery - There are 173
      Churches - 13,000
      Members - 3-4 Million
 See PC(USA) - Presbyteries, Synods and Other Links of Interest

Links:
Presbyterian Organization
Officers
Office of the General Assembly (OGA) | pcusa.org
Presbyterian polity - Wikipedia
The Barna Group studies religious trends
(United Methodist Women) UMW-Local Officer Job Descriptions