The max232 cable is needed to convert the -9V to +9V signal of a computer serial port to the 0 to 5V signal expected by the PIC. Once tinybootloader has been programmed into the PIC, this little cable is all that is needed to program new code onto the PIC. Here is the schematic. It is easy to breadboard up or you can make a more permanent cable with the chip built in.
The above schematic comes from the tiny bootloader website. Many thanks to the creator of this great tool.
I find that the Max232ACPE chip works well. It uses the smaller 0.1uf (104) ceramic capacitors, so it is easier to build into a compact circuit. Here is an example cable my digital electronics students built. Yes, that is a shotgun shell. It is a great case for small circuits/cables like this. If there is interest I can get a batch of printed circuit boards made for this cable.
I should soon have some more info and pictures of the actual build and test process, but the cable is really pretty simple. Just follow the schematic and it will likely work. You should probably breadboard the circuit on a solderless breadboard before you solder it up. Note that the PIC pins shown are for a different pic than the 16f88 and the RX and TX pins are on different pins.