[s1k3b8]

Systems programming concerns the code between hardware and the application programmer. So pretty much kernel programming.

Application programming concerns the code between kernel and the ordinary user.

Essentially, systems programmers write software that application programmers can interface with. Application programmers write software that ordinary users interface with.

It gets fuzzy at the edges like most definitions, but that's how I think about it generally.

[vnorilo]

I've always thought of compiler programming as systems programming. I guess it fits your definition of being something application folks interface with in addition to kernel.