It isn't always easy for some people (especially students) to get parts to learn more about using the Arduino etc. so I have a suggestion.
What would be the likelihood of anyone being willing to make an Arduino simulator?
Basically, you load up the simulator, plug in what you want to plug in on it (resistors, servo motors,thermonuclear reactors etc.) then upload the code you want to test so you can see roughly if your code/build is viable for what you want to do.
Obviously it would be good for people to still actually build physically things as much as they can. This suggestion is mostly because as a student, being able to afford luxuries such as this (an opportunity to learn more is sadly considered a luxury) somewhat puts a damper on being able to use it as a learning aid to its fullest.
Emulare allows me to simulate multiple Arduinos. I often simulate four at once (one as test_controller/data_collector and three as the system under test).
"Arduino Simulator" for Iphone/Ipod and Ipad, by Schogini, great simulator and continually improving, then there is Modkit which does exactly what is being asked for. Haven't tried emulare yet but will.
Take a look here http://arduino.com.au/Simulator-for-Arduino.html and let us know what you think. This Simulator only simulates the Arduino board so there is no option of adding resistors - Virtual Breadboard may allow that but there are mixed reviews for this and it costs somewhere around $29 from memory. With Servos, we just use an analog output which progressively becomes a darker shade of red. Thermonuclear reactors are best left for Tepco - those guys can get these happening without doing anything.
The Simulator for Arduino has just been upgraded to v0.97B for Pro Users and there are many fixes and improvements - Free Version upgrade available now - the free version has a 30s delay on opening a sketch (increments by 1s each time) and is code limited to 100 lines. Most of the Official Arduino sketches are included and there are many user sketches sent in for testing. Almost 850 Pro Users so far this year.
With the other Simulators, the Schogini iPhone app is pretty useless - I think the only change allowed is to change the delay between LEDs coming on. Looks good and works well as a training video but not really a learning tool. Had a quick look at Emulare but looked too hard to get going and not many people use 4 Arduino boards at the same time - also Emulare simulate AVR code not the special functions used by Arduino so not really an Arduino Simulator at all.
While the Simulator for Arduino is not perfect, it does have some great features such as auto opening the Serial Monitor and being able to step into custom library .h and .cpp files, as well as changing the font for the sketch by selecting Edit. Looking at the list of topics, it looks like our Simulator for Arduino may be behind some of the last few requests for suggestions on this forum.