Browsing through Thrift’s whitepaper (PDF), I’m still trying to completely understand it. It appears to provide a consistent way for different programming languages (PHP, Python, Ruby, Java, C++) to communicate with each other. In other words, it lets you build a web application by using the best programming language for a particular task, then tie the pieces together in a clean way.
I think Facebook’s site is the best testimonial that Thrift framework could ever get. I’ve been using the social networking app for awhile now, and it’s always fast, and always online (compare that with MySpace). Hopefully some other entrepreneurs will be able to make good use of this tool too.