Reminds me of an old idea I always liked and still haven't seen although it's trivial to implement: a contextual hotel search (admittedly inspired or at least stimulated to think about by the now very defunct Auction Ads - an eBay contextual ads network).
Say for Bratislava hotels you could send dates and a location as a parameter to display a selection of hotels in a given area available on certain dates. There could be any number of optional parameters. Obviously, there are more than a few websites that could implement something like this on a global scale in days not to mention Google itself.
These contextual ads could be shown alongside event information - for conferences, concerts, sports events, etc.
We've blogged about Zemanta, the Slovenian startup on the experimental Pizza SEO blog before.
