>        I also have a little LED project and was looking for some help with
>it. I'd like to build a box which determines the order of finish of a pine
>box derby <snip> 6 7-segment LED's which will show the position
>in which the cars finished <snip>

        You can simplify things in one of two ways... dump the 7-seg LED's
and just use 36 discrete LED's as follows (example):

Car # >         1  2  3  4  5  6

Position   1st        X
           2nd  X
           3rd              X
           4th     X
           5th           X
           6th                 X

        Or... interface your PIC's serial port to a PC and use either a dumb
terminal program or some quick and dirty program to display results.  The
only problem with this will be performing RS-232 level conversion.

>        1. Can anyone recommend a good IR TX/RX pair which is small, cheap,
>and will work over distances of about 3". Also, how do I wire this thing up?
>Do I just treat it as a normally open switch?

        I have had good luck with IR pairs from Radio Shack... about $2 or
$3 a pair.  If you use an IR detector you'll have to drive the base of an
NPN switching transistor (15 for $3 at RS) in order to amplify the levels as
follows:

        +5   +5
        |     |
        /     /
        \     \_________ Active low
        /     /          input to PIC
        \   |/
        |___|
        |   |\
     IR V     |
        -     |
        |     |
       ---   ---
        -     -

        Even cheaper and easier is to use CDS photocells from Radio Shack
and just use the AD inputs of a PIC16C74.  Look for a sudden drop in light
levels (increase in voltage):

        +5
        |
        /
        \
        /
        \___________analog input to PIC
        |
        |
   photoresistor
        |
       ---
        -

        Pick your resistors experimentally.  Place the photoresistor so that
the car passes over it.

        Have fun...

                                        - Barry