www.microchip.com, the makers of the PIC processors. Get the PIC16F628 datasheet, and the MPLAB Development software (assembler and IDE).

NOPPP, the "no parts" PIC programmer, including schematics and software.

http://people.man.ac.uk/~mbhstdj/, source for David Tait's "fpp" programming software. This is very flexible, able to work with a wide variety of programming hardware.

www.melabs.com, makers of the LAB-X3 prototyping board, and the picproto18 boards, as well as parts kits containing voltage regulator, crystal, and capacitors to get you going.

www.piclist.com, a discussion group on all things related to pics

vikon.com, another (possibly cheaper) source of the LAB-X3 board.

Digikey, source for all kinds of electronic items, including PIC chips, MAX232 chips, connectors, crystals, capacitors, whatever.

Texas Instruments, maker of the MAX232N chip. Search their site for the datasheet.

Halted Supply Co, a local (to me) electronics store with lots of goodies. I love searching their back room bins for oddball connectors, headers and such. They also have cheap LCDs and various surplus items. Their web presence isn't so wonderful, however, and I've never dealt with them except by visiting the store.

Smarthome, sellers of lots of home automation stuff, including CM11A and X-10 modules.

X-10, builders of X-10 stuff. If you're half as annoyed by their pop-up ads as I am, you won't even think of giving them any money directly, but the free ActiveHome software may be downloaded from http://www.x10.com/support (requires javascript). The RS-232 protocol for the CM11A is documented here.