I, as a complete nerd, enjoy messing around with logic circuits in programs like Yenka. I wanted to see if I could make a program like that in Flash, and I can't! I came quite close though, it can do most things I wanted. It just doesn't have saving, and has several bugs such as it falling foul to the race condition.
Anyway, here it is. If you find any bugs, can you tell me what you did to get the bug so that I can try and fix it.
Click on the tabs at the bottom to open a tool menu, then click and drag a component onto the stage.
Hold shift and click on a placed component to start wiring, and then click on a component to output to to connect them.
Hold alt, then click and drag to move placed components. This is quite buggy.
Hold ctrl and click on a component to remove it.
Some components (like switches) can be clicked on to change their output.
http://spamtheweb.com/ul/upload/100509/6 2430_main.php
Have fun (or not).