modifying a celeron to run as a dual processor

Tiny insulated wire, as thin as possible. I used 30 guage insulated wrapping wire (radio shack PN 278-503)
Vice pin drill and 0.5mm bit. This should be easily obtainable with appropriate (and smaller) bits at a decent art supply store. I bought mine at "Pearl Arts and Crafts" located in Central Square, Cambridge, MA.
A good soldering iron, with a sharp tip.
Solder
Desoldering braid, for those extra bits that you may accidentally leave
X-acto knive, if you plan on changing your cpu's core voltage
Masking tape
Multitester which can identify closed/open circuits, i bought mine at radio shack
A good magnifying lens may be of help for some of the small work

First verify that you can get each cpu operating at the desired clock rate in UP mode. Install one cpu in the first cpu slot and the cpu terminator in the other. Set your FSB to the desired setting (intel recommends 66mhz, some people have used 100mhz and above). If you plan on exceeding spec, you may also need to alter the cpu's voltage. [future link for that]. Make sure both cpu's run at the same core voltage.

Identify BR#1 on your cpu. take off the heat sink connector exposing the back of the cpu, with the ceramic cpu package facing TOWARDS you and the slot one connectors facing down. Start from the lower right of the cpu pin grids and count 12 vias (solder connects) up from the bottom. pin BR#1 is the middle one. Use a multimeter to verify that you don't have any shorts with nearby contacts.
Identify RP6 on your package, it will be on the same side in the upper right near one of the heat sink holes. It is labelled.
Solder a wire from BR#1 to the upper right pin of RP6 Solder the upper three legs on the left of RP6 together

Solder one end of another wire to the upper right pin of RP6, run the unsoldered end through the heat sink hole.

Identify ping B75. It is right near the gap (look for the B74 label). Put masking tape over B74 and B76 to make soldering easier. Solder the wire that you ran through the heat sink hole from RP6's upper right lead to B74. Verify that this isn't shorted with B74 or B76. Depending upon your multimeter, you may get a capacitance report. You should NOT get a connected circuit, though.

Identify BR#1 on this side of the board. Again, it is in the middle, twelve via's up, but on the LEFT. Using a 0.5mm (or so) drill bit in a hand drill. Drill out the metal contact. Don't go too deep, you just need to disable the cpu's contact with the board. A simple way to know: if it POSTS, then it is correct, else it is not.