I want to be able to attach a file that I generate (on the fly, I dont want to save the file on my server) and send it out via email.
I have the text all done, but I
You should be using Action Mailer that's built into Rails which supports sending emails with attachments.
For Rails 3.x - http://guides.rubyonrails.org/action_mailer_basics.html#sending-emails-with-attachments
For Rails 2.3.8+ - http://guides.rubyonrails.org/v2.3.8/action_mailer_basics.html#sending-multipart-emails-with-attachments