Salesforce Ideas is Generally Available! If you are using Professional, Enterprise, or Unlimited Edition, it is included so give it a try.

For new customers signing up for trial accounts, Ideas will automatically appear in the AppExchange drop down. For existing customers your administrator will have to activate Ideas. To do so go into Setup > Customize > Ideas > Settings, and you can click on the check box to enable Ideas.

Once you get Ideas Enabled, here are some recommended resources to help you roll out Salesforce Ideas.