how do i create a grid of cards with angular material?

I just needed this; here's a more comprehensive solution, only using the layout features, for 3 columns:

<md-content class="md-padding" layout="row" layout-wrap>
    <div flex="33" ng-repeat="i in [1,2,3,4,5,6,7]">
        <md-card>
            // ...
        </md-card>
    </div>
</md-content>

The card must be wrapped inside a correctly-sized div to keep the margins under control and avoid overflow.

I have created something similar to what you may want. The md-card is wrapped within a div having layout-wrap. The divs are dynamically generated after reading.

Here is the code :

<div class='md-padding' layout="row" layout-wrap>
    <md-card style="width: 350px;" ng-repeat="user in users">
      <img src="http://placehold.it/150x150" class="md-card-image" alt="user avatar">
      <md-card-content>
        <h2>{{user}}</h2>
        <p>Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua</p>
      </md-card-content>
      <div class="md-actions" layout="row" layout-align="end center">
        <md-button>Save</md-button>
        <md-button>View</md-button>
      </div>
    </md-card>
  </div>

The cards width can be adjusted with inline styling, hope it helps.

To be compling to material/angular, you must use flex attr to md-card. Flex attr will give you a proportional width about its parent.

<div class='md-padding' layout="row" layout-wrap>
    <md-card flex="40" flex-sm="80" ng-repeat="user in users">
      <img src="http://placehold.it/150x150" class="md-card-image" alt="user avatar">
      <md-card-content>
        <h2>{{user}}</h2>
        <p>Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua</p>
      </md-card-content>
      <div class="md-actions" layout="row" layout-align="end center">
        <md-button>Save</md-button>
        <md-button>View</md-button>
      </div>
    </md-card>
  </div>

In this example, you will have two cards (40% each) and when the screen resizes to -sm, the cards will be at 80%.