If the Journal is indexed by The Institute for Scientific Information (ISI) and has an Impact Factor, then you will find the most recently available Impact Factor on the journal homepage on http://springer.com.
Go to http://springer.com and look up the journal you are interested in by using the search box. Then, click on the journal to go to its home page.
The Impact Factor is shown on the left hand side of the the journal's homepage. Example: "Journal of Geodesy".
Information on the Impact Factor (where available) is now also displayed on the journal's homepage on http://link.springer.com