Well, you could always look up the opcodes for each machine language instruction, and the microchip .hex file format and write your code in a text editor... but I'm guessing that you probably don't want to get quite that "bare bones".
Alternatively, you can presumably write your C code in any text editor and then compile it using PICC Lite (a freeware compiler, available from Microchip) and then compile it using command line options.
These are both kind of silly options since MPLAB makes doing both of these tasks much easier... maybe you want to avoid C or assembly language all together... in which case I would recommend PIC BASIC Pro or PIC BASIC (I much prefer the pro, even though it is more expensive) from
www.melabs.com
They also have their own IDE... MicroCode Studio, I believe it is called.
Jason
P.S. If you can possibly run MPLAB, I recommend learning to use it... some of the emulator and debugging functions are quite useful.