HI-TECH Software has a freeware C compiler called PICC Lite, it is a full-featured C compiler but code size is limited to 2048 words and targeted only to some selected Microchip devices including the 16F877.
While we're on the subject, how about free or open-source compilers (not assemblers) for the 18F452? The part's about the same price, but it's newer & more capable than the 16F877. "C" or Forth tools would be nice, even in limited demo versions.
Although not totally free, this guy has some very interesting compilers as shareware: [urlhttp://www.picant.com]Pavel's Page[/url]
He has C, C++ (the first C++ I've ever seen for a micro) and Pascal. With more attention we might persuade him to keep on developing his compilers.