[paulrpotts]

Have you seen the game called Human Resource Machine?

This is not actually a joke comment -- it teaches assembly language programming. Not 6502 specifically, but the fake architecture looks a lot like 6502. You work up through a set of more and more challenging assignments until you have to write a sort. I really enjoyed it and would consider it a great introduction to basically any assembly language.

[crystalPalace]

I had never heard of Human Resource Machine but that reminded me of TIS-1000 which I highly recommend.

[dmcginty]

Thanks for the recommendation; I just purchased it. As another commenter said, TIS-100 is also a great game about an assembly language for a fictional computer that I'd highly recommend. I had a lot of fun playing with MIPS assembly in college, and I'd really like to do it again.