From FRA, there are commuter and long distance train stations right in the airport. Wiesbaden and Mainz are nearby.

VIE has a newish train, nonstop IIRC, to a downtown mall.

LIS is a cheap taxi ride, about fifteen Euro, if the cab driver doesn't try to scam you.

BCN has a cheap public bus to Plaza de Cataluyna right in the center, with a couple stops along the way.

The NCE airport is close to Nice.

AMS has a train station in the basement of the airport. Downtown is cheap and fast, with frequent
service, but the Hague and other nearby locations are also cheap. Downtown service runs every ten or fifteen minutes, with trains to the Hague etc. about twice an hour.

LHR is cheap if you take the tube, about an hour, or there are fast but expensive alternatives depending on your destination within London.

DUB has a cheap public bus that makes several stops in the downtown area.

Bergen has a cheap public bus.

Prague has a cheap public bus to the train station.

From CDG, the RER is expensive but convenient if your hotel is near a RER station on the line from the airport. There's also the bus to Opera plus several bus lines operated by AF, for example to Gare de Lyon and Montparnasse, with Orly service too. It's good if your hotel is within walking distance. Transferring to a metro line is miserable if you have luggage as most stations require stairs. The time required is generally an hour or more.