Germany for 2 weeks

Neuschwanstein "Schloss and castle" is the same and difficult to go by train as there is no train.
Daytrips from Frankfurt to Heidelberg and Baden-Baden is possible but what about after Munich, passing by the above castle and then go to Baden-Baden, north to Heidelberg ending in Frankfurt?

But to add to #1, there is a regular bus service from Füssen to Neuschwanstein, however it is south of Munich while Baden Baden is north. Füssen really is a full day from Munich- allow at least 2 hours travel each way, and the queues to get in to the castle on busy days can be an hour or two long - you will be issued with a timed ticket.
Your itinerary is doable but depends on what you enjoy as to whether it is worthwhile- for example, the slow train between Frankfurt and Cologne goes along the the Rhine valley without stopping. There is a great deal of Germany between Dresden and Munich which you'll miss - have you checked a guidebook? - but if that's your choice fine.
Why fly in and out of the same airport- can't you fly into Frankfurt and home from Munich or Berlin and then adjust you itinerary to give you more time in Germany?

Five cities in 2 weeks......plus the day trip to Neuschwanstein.

Too much for me.....too fast.

Then...depends of course what you want to see and do in each place.Your likes/interests....

Also,all your places are big cities (exc.the castle)...there is a lot more to Germany than that.

I'd personally look at something like Berlin and around,Dresden and Munich plus a little of Baveria.That is plenty for 2 weeks........or else,the places in the western part of the country (though for me that area is considerably less interesting).

Agree with mike on the open-jaw as well.....particularly if you want to travel all over the country.

Fly into one city and out of another......

To find out about travel time and costs http://www.bahn.de/i/view/USA/en/index.shtml tickets go on sale 92 days before, for the best deal book then, but you have to stick to the booked train or loose your ticket.

General information on train travel in Europe http://www.seat61.com/

If you want to make Frankfurt or Mainz your base for some days you could also do a day trip to the middle rhine valley and skip Cologne, go directly to Berlin from there.

Frankfurt - Berlin - Dresden - Munich - Neuschwanstein seeing Baden-Baden and Heidelberg on the way back to Franfurt would be best like regards wrote, it's a lot of moving, doable yes, enjoyable??

Open jaw or multi city ticket would be a good option as others suggested.

Day trips waste half the day, just getting there and back to your prepaid bed.

What if point B is cheaper, safer and more fun, than point A?

Pack only three compleat changes of clothes. We don't change everything every day. Hostels have washing machines.

And you'll need a day to relax. And mull over the constant sensory overload.
Even translating brit to yank.

Doable ? Sure. Frankfurt-Cologne is 2 hours; Cologne-Berlin 6 hours; Berlin-Dresden 2 hours; Dresden-Munich 5 hours; Munich-Schloss Neuschwanstein 2 hours; -Neuschwanstein Castle-Munich 2 hours; Munich-Frankfurt 4 hours. Total 23 hours travel time out of 14 days, gives you plenty of time to sleep and even have a warm meal every day.

Whether this makes sense, I leave this decision to you. But sometimes less is more.

Train is a fast, comfortable and reliable mode of transport. If you qualify for a German Rail Pass also cheap (only available for travellers from overseas) Look here: http://www.bahn.de/i/view/USA/en/prices/germany/german-rail-pass-southern-germany-promotion.shtml?dbkanal_007=L16_S02_D002_KIN0001_kv3-grp-south_LZ001 Generally www.bahn.de is THE one and only website for info and booking, all infos come in english too.

If this does not work and you find train tickets at regular prices bit too costly, look at long distance buses like www.meinfernbus.de might be an alternative. The bus net is growing rapidly so by next year it might be plenty of choice. Buses however will be slower than the train.

Believe it or not, I'd actually cut out Berlin and Dresden. I wasn't in Dresden, but I was in Berlin. And Berlin is a wonderful city, but it isn't terribly German. I enjoyed much more the Black Forest region.

Try this:
1 - Fly to Frankfurt
2 - Day trip to Cologne to see Cathedral and Greco-Roman museum that is adjacent. Take train to Aachen to see cathedral and Charlemagne's remains. Return to Frankfurt.
3 - Frankfurt
4 - Heidelberg Castle - Sleep in Karlsruhe
5 - Day Trip to Triberg (really cool town with cuckoo clocks everywhere), and then spend rest of the day in Baden-Baden
6 - Day Trip to Strasbourg, France (AMAZING)
7 - Go to Media Musem in Karlsruhe and then head over to Stuttgart in the afternoon to sleep
8 - Porsche Museum/Mercedes-Benz Museum/Stuttgart Art Museum
9 - Bebenhausen/Tubingen - Evening Train to Munich
10 - 11 - Munich
12 - Neuschwanstein
13 - Day Trip to Regensburg or Nuremberg
14 - Fly home From Munich!

Very doable by train. This would mean 13 nights/14 days. If by 2 weeks you meant 14 nights, I would take a day trip from Frankfurt to Worms. Or take a day trip from Munich to Salzburg, which looks extremely do-able.

This is extremely accessible by train and it is a lovely itinerary. This accounts for 3 nights in Frankfurt, 3 nights in Karlsruhe (which as a town is unimpressive, but serves as an excellent satellite town to take day trips from), 2 nights in Stuttgart, and 5 nights in Munich