Microchip – manufacturer of PIC Microcontrollers
http://www.microchip.com
Microchip Sample – Request free PIC samples
http://sample.microchip.com
Piklab – Nice IDE for Linux (open source)
http://piklab.sourceforge.net
SDCC – C compiler for PICs and other microcontrollers (open source)
http://sdcc.sourceforge.net
HI-TECH – One of the best PIC C compilers around (free version available)
http://www.htsoft.com
Rau Deaver – Some nice links for PIC programming on Mac
http://www.rau-deaver.org/
Elettrolinux – A good selection of open source projects for electronics
http://elettrolinux.com/