I think in the Soprano's they were mostly loan sharking, or "shylocking".
"Protection money" kind of fell out by that point, but they still were getting guys wrapped up in debt and then chasing them down for it. Tony's highschool friend who owned the sports store is a good example of that kind of thing.
At that point in time in real life, there still were residuals of the mafia, but definitely not as powerful as they used to be. The smart guys at the top who survived RICO managed to basically move their money into clean ventures. And all of the lower down guys made their way into controlling municipal permits, infiltrating unions and getting their feet into local police forces. More boring shit like that basically. Some got into the drug trade but that starts to become an entirely different story.
Basically think of the Esplanade project and the no show jobs and how big of a deal that became for Tony's crew. That type of stuff was the future of the mob at that point.