Can't get Gulp to run: cannot find module 'gulp-util'

UPDATE

From later versions, there is no need to manually install gulp-util.

Check the new getting started page.

If you still hit this problem try reinstalling your project's local packages:

rm -rf node_modules/
npm install

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OUTDATED ANSWER

You also need to install gulp-util:

 npm install gulp-util --save-dev

From gulp docs- getting started (3.5):

Install gulp and gulp-util in your project devDependencies

If you have a package.json, you can install all the current project dependencies using:

npm install

Any answer didn't help in my case. What eventually helped was removing bower and gulp (I use both of them in my project):

npm remove -g bower
npm remove -g gulp

After that I installed them again:

npm install -g bower
npm install -g gulp

Now it works just fine.