I have been loving YQL ever since I figured out how to use it to scrape webpages and return the data as JSON – allowing you to turn any standard web-page into a simple API ..opening up endless possibilities for data mash-ups.. IMO, its the best thing Yahoo has ever produced!
I wrote a little jQuery plugin that uses YQL to convert an RSS feed into a handy JSON object – this tiny extension makes its easy to work on rss feed mashups and widgets.. just check out this instagram tag search or this gimmebar user feed that i made in a matter of minutes..