Time is near to depart the US and my wife and I are in the final stages of identifying transportation options while in several urban areas. I would be grateful for information on the best 4 day pass for Paris, Munich and Bremen, and 1 day pass in Hamburg. We will be using the Metro, UBahn, trolleys, etc in the cities as well as local trains to nearby destinations: Paris-to Versailles, Chartres, Munich to Salzburg, Fussen, Dachau, Kloster Andechs; Bremen to Bremerhaven, Oldenburg, Achim and Verden. We will always be together so if there is a bargain on a pass for two people traveling together, this would be good. If a 5+ day pass is a better deal (perhaps including admission to museums, etc), we could use it for 4 days and give the unused day(s) to someone as we depart the city.
There is not a uniform answer to all those cities. Every cities has a different arrangement for all day passes. Some restricted to after 9 AM, some pairs, others for families, some go for 24 hours and other expire at 2 AM, etc. If you don't find that information in a tour book, head for the nearest TI or local ticket and they will explain your options.
In Paris I would get the ten-ticket "carnet" deal and use the tickets for individual journeys. Day passes in Paris are very poor value for money compared to many cities: you will only save if you make at least six journeys per day. (Paris single tickets allow unlimited changes in the same direction between Metro/RER lines and bus/tram routes, but you need a new ticket to change between rail and road modes.) Definitely avoid the over-priced tourist-trap Paris Visite passes. Also note that Chartres is well outside the Paris ticket validity area, so you will need to buy a specific rail ticket for that journey.
I agree with Philip about Paris. Buy ten-ticket carnets (€12.00) as needed and share the tickets. Each t+ ticket is good anywhere the metro goes (some lines end in zone 3) and on the RER in zone 1 (all of central Paris). If you're only going to be in Paris for four days, then I suggest that you visit Versailles and Chartres on the same day (if you visit them at all). Versailles is in zone 4. Buy a single ticket (€3.05) that will cover your ride on the metro and the RER C to Verailles-Rive Gauche and spend the morning at the chateau. Take a regional SNCF train from Versailles-Chantiers to Chartres (€11.80) and eat a picnic lunch on the just-under-an-hour ride. Visit the cathedral in the afternoon and then take a SNCF regional train back to Paris (€14.00).
For Munich, you can probably use local passes for less than a day of a railpass. For Salzburg and Füssen as day trips, use the Bayern-Ticket, and all day pass for regional trains for €29 for two people. Valid after 9 AM workdays. For Munich, use Partner Tageskarten, all day tickets valid for all conveyances of the MVV (Munich metro). Use a Munich XXL Partner Tageskarte valid for the inner two zones of the MVV for €12,80. For Andechs use the Gesamtnetz Partner Tageskarte for €19,60. Both cover the S-Bahn and the bus (check the schedule for Andechs. Only some S-Bahn are met by the MVV bus, which is included. Other S-Bahn are met by private buses, for which you pay extra).