Going forward with an idea discussed in my other blog - there is a need for a search engine which enables transaction. Some ways in which this can be done is use google, yahoo, msn search APIs for the first level search service. Then have a static list of transactional services providers like Amazon, Ticketmaster, Priceline, eBay, etc. If the search result contains any of these urls then clicking on the url will take the user to another page (owned by the search engine) where they can complete their transaction. In future try to generate the list of transactional service providers dynamically.