npm list
npm ls
This command will print to stdout all the versions of packages that are either installed or available in the registry, with their tags and whether or not they're active and/or stable.
To filter a single package or state, you can provide words to filter on and highlight (if appropriate). For instance, to see all the stable packages, you could do this:
npm ls stable
Another common usage is to find the set of all packages that are installed. This can be accomplished by doing this:
npm ls installed
Strings are matched using the JavaScript "split" function, so regular expression strings are ok. However, the highlighting is a simple split/join, so regexps probably won't get the funky colors.