Emailexample is a project mainly written in Ruby, it's free.
Heroku / Sinatra / Email Collection
I was thinking about this post: http://news.ycombinator.com/item?id=1568298
I don't like the Google branding, either.
I figured out how to do it from this post:
http://ididitmyway.heroku.com/past/2010/3/30/superdo_a_sinatra_and_datamapper_to_do_list/
One thing of note, you should change this in main.rb:
get '/all' do @emails = Email.all erb :show end
It's obviously unsecure. If you're not too worried, you could simply obfuscate it and make it a really hard to guess URL ... or get fancy and put some authentication around it.