Just about every PHP programmer has heard of or used Smarty Templates.
I had heard of it a long time ago, but only just recently started using it. For the longest time, I have been using good old phpLib’s Template.inc. It is simple and suits most of my needs. But it’s quite old. I’ve been using it for like 7 years.
A colleague of mine convinced me to try out Smarty. I used it to create a new RSS feature for PaperDemon.com’s blogs (and also added an RSS feed for my blog on BogusRed.net as well, subscribe to me!). I did it using Smarty because it seamed like a good thing to templatize and also because Smarty has a really good caching system. So if people’s RSS readers are constantly pinging the RSS feed pages, the PHP won’t have to pull from the database every time. +1 for performance!