See:
http://www.tech-tools.com
and look for CVASM. Assembler that uses 8051 like opcodes for the PIC. These are expanded into one or more PIC opcodes by CVASM. CVASM is formerly known as PARALLAX assembler. You can find PIC source written in that too. Tech-tools offers a free CD, which is worth having (nice app notes, demos etc.).

If you are seriously into PIC development you may want to subscribe to piclist for all your PIC related questions.

http://www.piclist.com/techref/piclist/index.htm

Regards,

Dincer Aydin
www.geocities.com/dinceraydin/