I loved Scheme in the programming languages concepts class I took several years ago. Ever since reading what Paul Graham has to say about Lisp, I've been intending to go back and pick Scheme up again and see if it'll improve my programming in general.
Are there any well-known works of software written in Scheme? Open source packages? Websites?
It is (was?) used as a scripting language in some open-source packages software, such as The GIMP. There are also some GNU projects that use Guile (a Scheme implementation) as their scripting language.
Some programs are not directly written in scheme but provide scripting capability through a scheme interpreter. Some examples are the gimp and the window manager sawfish.
I'm pretty sure ITA Software uses Scheme for most of their algorithms.
The Jak & Daxter series of games were written in a Scheme-like custom language called GOAL. A lot of Schemey features like garbage collection and dynamic list allocation had to go out the window to make it run in constant memory and time, but it's still recognizably LISPish. The GOAL compiler was written in Commmon Lisp.
There is a framework called lambdanative that is used to create cross-platform applications for ios, android, linux and windows systems. The code for the applications is written in scheme which is later translated to C using Gambit-C which then uses the SDKs of the various platforms to compile for them. Its a great use of the scheme language and could still go a long way.
So there are plenty of apps written in Scheme using this framework.
Also, emacs makes heavy use of its own dialect of lisp called Emacs Lisp. That is pretty related to Scheme, since Scheme itself is a dialect of Lisp.
The Haxima game engine is written in Scheme and the Nazghul game, also in scheme, runs on it. Both are Free Software so you can actually study or even modify the code if you like.
Two that I am aware of personally: Whilst working at a telco, we installed a middleware product, basically a message router, that was written is Scheme, and used "schemelets" to identify and translate messages. That was my first exposure to it.
The second was a certain suite of compilers and IDEs (I can't mention the company or product for various reasons but they came from before the age of visual tools :-).
