Google Docs are awesome and there are a lot of things to learn about them. Here is a tutorial on how to add a dropdown to Google Spreadsheet
Step by Step:
- Select the cell or cells where you want to create a drop-down list.
- Click Data and then Data Validation.
- In Criteria, choose the option, List of items
- Enter items, separated by commas and no spaces.
- Click Save. The cells you have chosen will show a dropdown list of the items you created