This project contains a 6502 CPU emulator called fake6502 from http://rubbermallet.org/fake6502.c wrapped in a very simple Virtual Machine to aid learning to program the 6502 processor. This is a very hacky and quickly put together project and is certainly not even close to production quality but you may find it useful.
I started with DASM to generate 6502 object code but it quickly became apparent that this was a slow way to learn as it required having to include the DASM assembler in the development cycle. I therefore implemented support for simple hex files which quickly evolved into a very basic mnemonic syntax with limited support for labels (they have to be defined before used so are only really useful for jumping backwards but that stops you having to calculate the two's complement relative jumps yourself). You can control some aspects of the VM's operation too from the hex files including setting breakpoints.
To interrupt program execution, just use CTRL-C and you can then step the processor, place watches and breakpoints. I have posted this on GitHub as I wrote it to help me learn 6502 machine code as I couldn't find anything else I particularly liked. Some of the design of this tool is rather limited and there are clearly inconsistencies but please feel free to fork and take it your own way or suggest pull requests.
I will add documentation over time but the best way to learn the operation of the tool is via the comments in main.c.