The first thing that I noticed when I was looking for websites that would explain American politics in a simple, easy-to-understand way is that there aren't any.  I think that this reflects the true nature of American politics.

Most of the information that I found that would be good for ESL students is at:

History Central
http://www.multied.com/index.html

Within this website, there were many interesting areas, including:

ElectionsCentral-A History of Presidential Elections
http://www.multied.com/elections
This website can give you information on the electoral college, the history of presidential elections, and more.
It can help answer some questions like this, and may help you understand the presidential election of 2000:

• Did you know that a candidate does not win the presidential election in the United States by a simple  majority of votes?
• What's the difference between the popular vote and the electoral college?
• Are there any other political parties in the U.S. besides the Democrats and the Republicans?
• What have past elections been like?
• What is voter turnout?  What's voter turnout like in the U.S.?
• What are polls and what do they mean?

Civics Vocabulary
http://www.multied.com/Civics/index.html

American Wars
http://www.multied.com/wars.html

Middle East
http://www.multied.com/Mideast/index.html

During the last election, the strongest third party candidate was Ralph Nader.  Here are two websites where you can read articles about some of his opinions.  (Advanced reading and vocabulary)

Ralph Nader in the Public Interest
http://www.sfbg.com/nader

Public Citizen
http://www.citizen.org
 

Here's an interview that came out right before the last election where you can compare the two presidential candidates, Al Gore and George W. Bush.  It has point by point comparisons of their opinions on various issues:
http://www.readersdigest.com/rdmagazine/oct00/candidates.asp

You can try looking in Dave's ESL Cafe's search engine:
http://eslcafe.com/find
When you get to this page, choose SOCIETY.  When you get to the next page, choose POLITICS, and choose topics from there.

You can also try:
The White House
http://www.whitehouse.gov
 
 

ANOTHER GOOD SOURCE OF CURRENT EVENTS, INCLUDING NEW SUMMARIES, IS THE
New York Times Web Summaries Website
Click here for more information and the link.