simpleCart A Free and Open-Source Javascript Shopping Cart

Now that I'm starting to step into web development, I'm always getting introduced to new  things, especially with things that as a Web Designer I've been using for years but never actually knew how powerful these things were.
One of those things is JavaScript, the more I learn about it, the more I realize I don't know.
I was really blown away by this new shopping cart I came across, it's called simpleCart, a completely free and Open Source shopping cart completely written in JavaScript.
The UI is very responsive and smooth, it works with PayPal, Google and Amazon payment gateways.
It's very well documented and has new features being added, if you want to build a simple shopping cart solution for a client then this is something new to try out.
Since it's based in JavaScript, It's quite easy for a user on the client side to just change the price of an item in the source code on the page. To void could either validate it on the server-side, which is simple enough.
Apart from that this works great.
Check out simpleCart.