Another apparent web trend, but really just designers getting rid of the unwanted flashy taking a more minmal and less intrusive approach. I've been doing it myself on personal site's for some years now, but Flat Design is taking over the web at a very fast pace. It's great, I've been coding up some cool looking websites which are coming this 2013 Australian Election.
The only problem I've found with Flat UI Design is the lack of direction for users, I've found taking out gradients means there is less depth in the design for users to gauge the difference from a button and a link, but it also come down to just some minor CSS adjustments to give the users a que that they are on a button or link.
Now I'm a huge fan of reusing, I like Designmodo Flat UI
It's full of resources for you all to begin your Flat Design.