Testing changes to npm package locally

gistfile1.txt

For Example:
cd ~/projects/node-redis 
npm link                 
cd ~/projects/node-bloggy
npm link redis             # links to your local redis

To reinstall from your package.json:
npm unlink redis
npm install

sudo npm rm --global foo
This will uninstall the package.
To check whether a package is installed, the npm ls command can be used:
npm ls --global foo