The newest versions of KNIME (2.2 or higher) allow you to connect to a public server from which you can download workflow examples.
KNIME provides a new view called "Server Workflow Projects". On the screenshot below it is on the bottom right, highlighted by a red frame. If you have updated from an older KNIME version or in case you have closed the view, you can open it through the menu "View" - "Other..." - "KNIME Views" - "Server Workflow Projects".

The Server Workflow Projects view allows you connect to public KNIME workflow servers using a fixed guest account. Just simply press the connect button.
If you have KNIME Enterprise Server or KNIME Server Lite installed you can also connect to the public server. Use the following connection parameters:
Workflow Server: publicserver.knime.org
Username: guest
Password: guest
Once you are connected to the server you will see the workgroup directories of the server repository.

You can open the different workgroup directories and browse through the workflows or you can search for a specific workflow using the search box. Simply enter the ID (e.g. 002001) of the workflow you are interested in and press return.

The search filters out the appropriate workflow which can now be downloaded. To do this right click the workflow to open the context menu and select download.

You are prompted to select the destination in your local workflow projects and the workflow is downloaded from the server.
Important:
Check the meta information of the workflow. It contains useful background information for the flow and lists the required extensions that you need to install in KNIME in order to open and execute the workflow.
If you should have problems accessing the public server, for example, due to the firewall or proxy configuration of your network, you can also download all flows available on the public server as a zip-file.