The census held in the USA every ten years has an impact on the political geography of the country. At a Federal level the allocation of seats in the House of Representatives to each state changes - and district boundaries are redrawn to take account of the population shifts. In the Presidential Election the electoral college changes - as the numbers of votes in the college for each state must be "equal to the whole Number of Senators and Representatives top which the State may be entitled in the Congress" (Constitution Art II Section I).
The Census was held on April 1st - but the calculation of the figures takes several months. The "Form Delivery and Mail Back Phase" took from 3rd January to 16th April. There was then a "Door to Door Follow Up Phase" which lasted until 10th July. Quality Assurance Operations lasted from 11th April to 3rd September. The complete Questionnaire Data Capture and Processing began in May and ends in December. The 2010 Population Counts are due to be reported on 31st December. [By law the data must be delivered to the President of the United States by the Census Bureau on or before December 31, 2010].
States can then begin the process of redistricting. There is no uniform way of doing this - and some redistricting is in the hands of the state legislatures - which is why the 2010 state election results were so important. Some states do have independent bodies to recommend proposals.
So we don't yet know what the new map will look like - but estimates have been made. Election Data Services have produced their estimates - fuller details here - and suggest that the States which will gain seats are
Texas (4); Florida (2); Arizona; Georgia; South Carolina; Nevada; Utah and Washington
The potential Losers are
New York (2); Ohio (2); Illinois; Iowa; Louisiana; Massachusetts; Michigan; Missouri; New Jersey and Pennsylvania.