Sometimes new technologies or new techniques go straight into a project, sometimes they are used in a test first. Making a test first is a part of extreme programming (XP). If you are going to try something new where you don’t know how it’ll behave, it makes sense to try it out in a small application first where you can make sure it works.
I post tests and ideas on exp-sd.com, they tend to be graphical tests where I can post a JPG or movie to show what they look like. The website itself is a blog-like CMS website that I wrote myself in PHP.
PHP code examples at my Github page.
Very Old Tests
Very old server-side image upload website (2002-5) archive and info: jpeguploader.com