This is a simple tip which I have found very handy since I’ve updated my rails to 3.0.0 this week. If you need to generate a new project but need to use a “legacy” version of rails then you simply include the version within your code using this syntax:
rails _version_ projectname
So my current need to use 2.3.5 for a site uses this command line:
rails _2.3.5_ mysite
Small tip but big help for those like me who have to manage and support multiple versions of Rails across environments.