just an example of how you can poll reddit

reddit_polling.rb

require 'open-uri'
require 'json'

received_posts = [] # posts we've already received

loop do
  # get all of the current posts
  posts = open('http://www.reddit.com/new.json') { |f| JSON.parse(f.read) }
  posts = posts['data']['children']

  # get a list of new posts by taking the ones we just received and removing
  # the ones we've received before
  new_posts = posts - received_posts

  new_posts.each do |post|
    # put this one into the list of received ones, so we don't get it again
    received_posts << post

    post = post['data']

    # print out the title
    puts post['title']
  end

  sleep 60 # wait 1 minute before trying again
end