See the documentation for picprog-1.9.1 for information and links.
Download the latest version, dated 2010-04-14: picprog-1.9.1.tar.gz. It supports PIC16, PIC12 and PIC18 families, and compiles on Linux as well as on Windows with Cygwin Linux emulator. I have tested PIC16C84, PIC16F628, PIC16F676, PIC12F675, PIC16F88, PIC16F876A, PIC16F76, PIC18F1320 and PIC18F458. Other people use it with a lot of other types.
Older versions are also available: picprog-1.0.tar.gz, picprog-1.1.tar.gz, picprog-1.3.tar.gz, picprog-1.4.tar.gz, picprog-1.5.tar.gz, picprog-1.6.tar.gz, picprog-1.7.tar.gz, picprog-1.8.3.tar.gz, and picprog-1.9.0.tar.gz. Version 1.2 was so broken I do not offer it for download.