As of December 08, 2012, Google is no longer accepting sign ups for the free plan for their Google Apps service. However if you are an existing user, you can continue using the service without any charge. This will impact the new sign ups only. Here is their official notification:
Hello from Google,
Here’s some important news about Google Apps—but don’t worry, there’s no need for you to take any action. We just want you to know that we’re making a change to the packages we offer.
Starting today, we’re no longer accepting new sign-ups for the free version of Google Apps (the version you’re currently using). Because you’re already a customer, this change has no impact on your service, and you can continue to use Google Apps for free.
Should you ever want to upgrade to Google Apps for Business, you’ll enjoy benefits such as 24/7 customer support, a 25 GB inbox, business controls, our 99.9% uptime guarantee, unlimited users and more for just $5 per user, per month.
Thank you for using Google Apps.
Director, Google Apps