As a fan of alternative history (indeed an essay on it got me into Cambridge), I've got to say that Sealion is one of those annoyingly persistant What-ifs that never quite die despite having gigantic amounts of stuff written on them. Put simply, it wasn't going to happen, and if the Germans had been stupid enough to try then it'd have been a massacre. Why? http://www.flin.demon.co.uk/althist/seal1.htm is probably the best summary of why Sealion could never have worked. http://www.geocities.com/drammos/sealion1.html is a good take on the results of a failed landing.
Alternative history is fascinating stuff though, if you have an afternoon free then I recommend this masterpiece http://alternatehistory.com/decadesofdarkness/ . May as well plug my own efforts as well ;) - http://www.quarryhouse.free-online.co.uk/ed/Althist.htm
The massing of the invasion force would have compelled Roosevelt to send U.S Naval forces to the Channel. At this point the U.S. would have been at war with the AXIS partners and the status of our forces at Pearl would have also been different. Hitler made the war longer by not invading.
A major reason it was not put into effect was the armed Switzerland citizenry.
Thanks for the links. Interesting stuff.
bump for later