Software emulators have great value for the software developers who are focusing on high level application software. There are some popular open source emulators for embedded systems, like QEMU, ARMulator and Skyeye. Among these emulators, QEMU is most powerful one which can support many new features and Linux distributions. While Skyeye focuses on RTOS (uC/OS-II, VxWorks) and embedded Linux on the popular processors (ARM7TDMI, ARM920T, StrongARM and XScale, MIPS, 68K, ColdFire, Blackfin and PowerPC). Usually I choose Skyeye for the low-end embedded systems with RTOS and uClinux. 

Installation of Skyeye was a trouble process in Cygwin. As time goes by, the installation is much easier since I have installed an easy Linux distribution Ubuntu 8.04. You can just type following instruction to install the Skyeye:

sudo apt-get install skyeye

Then the system will prompt you to install the skyeye and its dependency components. Just comfirm it with Y(es) to continue. Some people claim some extra components have to be installed prior to Skyeye. You can install the components if you have enough disk space. These components are critical for source installation for Skyeye. However, I am a lazy person who chooses an easy default binary installation. After installation, you have to download the skyeye-testsuite from their project site. Decompress it to a dedicated folder and switch to the folder. You can find some brief documentations and Linux image and skyeye.conf file in each test subfolder. In general, you can just type skyeye in the subfolder, and wait the Skyeye emulator to run and bring up the Linux console. In other cases, you may type as following, which you may check out the information in the enclosed README file:

skyeye -e vmlinux -c skyeye.conf

In the test cases, you can find many different systems which have been confirmed to run on Skyeye, as well as untested systems. There are various systems, including uClinux (the first one which successfully runs on Skyeye) for ARM7TDMI, Blackfin and Coldfire, ARMLinux on S3C2440, uC/OS-II on ARM7TDMI, u-boot for MIPS/ARM/PPC. Usually the Linux OS will bring up the Shell console, so you can access the file system to check out how an embedded Linux operates. You also can try out the uClinux with MiniGUI. But I have to warn you that emulation (with GTK+) takes a long time. I will like to suggest you to develop MiniGUI applications for x86 then port to uClinux by cross-compiling and emulating on PC (with qvfb) , rather than emulating the whole system on Skyeye.

Of course, the emulated system and user applications can be debugged with GDB. You have to consult the documentation to find out how to setup everything (toolchain, environment and other tools) to work. 

Reference
http://www.skyeye.org/index.shtml