The public transport system, including buses, U & S-Bahn and ferries, is relatively easy to navigate for individuals with disabilities. Most stations have lifts that offer easy access to the platforms for wheelchair-users and the less mobile, find the list of barrier-free stations here. On the U & S-Bahn platforms, tactile markings direct visually impaired individuals to the doors of the train. Buses carry access ramps. On the trains, buses and ferries, there are special seating areas dedicated to wheelchair-users and people with special needs, and the upcoming stops are announced both audibly and visibly.
If you're staying in Hamburg long-term, you might want to request a special pass that allows people with disabilities and their companions to travel for free. Here, you'll find a German-language explanation of the so-called Schwerbehindertenausweis.
Plenty of Hamburg's museums, landmarks and activities are accessible for those with special needs. In front of the City Hall on Rathausmarkt, a bronze scale-model of Hamburg provides a fun way to gain a first impression of the city, both by touch and by sight. Take a look at this website for a map showing anything from parking spots and public bathroom facilities to the best wheelchair-friendly shopping and sightseeing routes around Hamburg.
The Fischmarkt markets, the Landungsbrücken piers, the Cap San Diego ship, St. Michael's Church, the Planetarium, the Planten un Blomen park and Hagenbeck's Zoo are some of the barrier-free highlights the city has to offer. In addition, most museums in Hamburg offer discounts to people with disabilities and their companions, and are barrier-free: e.g. Hamburger Kunsthalle, Museum für Kunst und Gewerbe, International Maritime Museum, Miniatur Wunderland, Deichtorhallen, Bucerius Kunst Forum, Hamburg Dungeon and Dialog im Dunkeln.
If you're visiting Hamburg and looking for a place to stay, there's a variety of accommodation that is barrier-free or otherwise suited to your needs. Search for hotels that are wheelchair-friendly and have lifts on this list by Hamburg Tourism.