Go to www.usgovernment.gov to find out just about anything about US Government. It does list all the "Departments", if by Department you mean Cabinet level departments. However it will take lots and lots of digging to get all agencies of the US, because there are agencies within departments and bureaus within agencies.
In the USA, Nebraska and Maine.
In the US it is the secret service. They are part of the Treasury Department. In other countries then various government or military departments carry out a similar role.
USA
If you are in the USA, you will find out on Jan 20th 2009
Chairman of the Constitutional Convention, Commanding General of the Army, and President of the USA
On Mission Xtra - 2009 Resort Ministries 1-7 was released on: USA: 14 March 2009
Outreach Connection - 2007 Prison Ministries 4-175 was released on: USA: 10 August 2010
Pastor Mike Online - 2011 119 Ministries - 1.148 was released on: USA: 28 February 2013
In the USA there are 356 Cabinet Departments
There are several online sites where one can find information and a list of Canon USA cameras. An excellent online site that has this information is "Canon-digital".
Outreach Connection - 2007 Brian Stone Ministries 4-165 was released on: USA: 1 June 2010
Pastor Mike Online - 2011 119 Ministries 1-148 was released on: USA: 28 February 2013
Divine Restoration - 2005 Grace Restoration Ministries Toronto 3-7 was released on: USA: 2008
Outreach Connection - 2007 Pastor Charles Sharpe - Heartland ministries - 2.90 was released on: USA: 2008
Outreach Connection - 2007 Jim Daniels Word Ministries 4-162 was released on: USA: 11 May 2010
Outreach Connection - 2007 Duke DuVall Light of the World Ministries 4-163 was released on: USA: 18 May 2010
Outreach Connection - 2007 Cindy Winters Grace and Hope Ministries 4-164 was released on: USA: 25 May 2010