Craiglist doesn't allow negative keyword searches. I fixed that.

negacraig.rb

#!/usr/bin/env ruby
require 'rubygems'
require 'nokogiri'
require 'open-uri'

bad_words = ["basement", "realtor", "finch", "eglinton", "scarborough", "brampton", "sheppard", "kipling", "islington", "markham", "lawrence", "steeles", "pape", "donlands", "etobicoke", "mississauga", "highway", "cityplace", "yonge", "mortgage", "consultation"]

search_url = "http://toronto.en.craigslist.ca/search/apa?query=&srchType=A&minAsk=&maxAsk=1000&bedrooms=&format=rss"

doc = Nokogiri::XML(open(search_url))

# unnecessary for greader to pick it up
doc.css("items").remove

doc.css("item").each do |entry|
  text = entry.to_s.downcase
  bad_words.each do |word|
    if !text.index(word).nil?
      entry.remove
      break
    end
  end
end

File.open("out.rss", "w") do |io| io.puts doc.to_xml end