list npm installed packages

For local modules:

npm list --depth=0

For global modules:

npm list -g --depth=0

If you'd like to see all available (remote) versions for a particular module, then do:
npm view <module_name> versions

Note, versions is plural. This will give you the full listing of versions to choose from.

For latest remote version:
npm view <module_name> version  

Note, version is singular.

To find out which packages need to be updated, you can use
npm outdated -g --depth=0

To update global packages, you can use
npm update -g <package>

To update all global packages, you can use:
npm update -g