An example sinatra app that uses pony and gmail to send an e-mail

contact.haml

.grid_12
  %h1 Contact
  %h2 Want to get in contact, have a question or just fancy a chat? 
  %p Fill out the form below
%form{:action => "/contact", :method => "post"}
  %div{:style => "margin:0;padding:0;display:inline"}
    
  %label{:for => "contact_subject"} Subject:
  %br
    %input#contact_subject{:name => "subject", :size => "30", :type => "text"}/
    %br
      %label{:for => "contact_email"} Email:
      %br
        %input#contact_email{:name => "email", :size => "30", :type => "text"}/
        %br
          %label{:for => "contact_message"} Message:
          %br
            %textarea#contact_message{:cols => "40", :name => "message", :rows => "3"}
            %br
              %input{:name => "commit", :type => "submit", :value => "Send"}/
%div{:style => "clear:both"}  

contact.rb

require 'rubygems'
require 'sinatra/base'
require 'pony'

class Contact < Sinatra::Base
  set :static, true
  set :public, 'public'

  get '/' do
     
    return haml :contact 
           
  end
  
  post '/' do
    Pony.mail :to => ENV['TO_EMAIL'],
              :from => params[:email],
              :subject =>  params[:subject],
              :body =>  params[:email] +" wrote:\n" + params[:message],
              :via => :smtp,
              :via_options => {
                  :address              => 'smtp.gmail.com',
                  :port                 => '587',
                  :user_name                 => ENV['GMAIL_USER'],
                  :password             => ENV['GMAIL_PASSWORD'],
                  :authentication       => :plain, 
                  :domain               => "yourdomain.com" 
                } 
    return haml :contact_response
  end
  
  
  
end

contact_response.haml

%h1 Your mail has been sent! 
%p Thanks for getting in touch