Google Apps for Your Domain has been launched in 2006 as a solutions for organizations that wanted to use Google's applications on their own domains. In 2007, Google launched a premier edition for businesses that added corporate features, APIs, phone support and service-level agreement for Gmail.
But how many businesses use Google Apps? A post from July mentioned that "500,000 organizations adopt Apps as part of their business, with another 3,000 signing up every day", while another blog post from October informed us that "more than 1 million businesses have selected Google Apps to run their business".
It's not clear how many of these organizations use the paid edition of Google Apps, but Google decided to make it difficult to even find the free version.
Here's Google Apps homepage, where you can only click on a big blue button:
The second page says that "Google recommends Premier Edition for businesses in the cloud" and invites to me start a free trial. There's a small link below the "Begin free trial" button that lets you use the standard version, but it's difficult to notice.
If you click on that link, you'll get the page that compares the standard and the premier versions, which used to be displayed by default.
Google Apps is now in the same league as RealPlayer, which shows a small link to the free version, while using the rest of the page to promote a paid version. Just in case the link to the Google Apps Standard Edition goes away, here's how to sign up for free.
Update (December 2012): the free Google Apps is no longer available for new users.