This board is probably one of the mose useful boards I've ever made.  It's simply a usb to serial converter with opto-isolation.  This has a few very important consequences:

1) Will not leech power into a circuit when you're trying to cycle power and watch boot-up messages

2) Will not fry your usb port when you fry your circuit

3) Means that you can have the voltages between the USB circuit can be totally different and all you have to do is change R16

The bill of materials is as follows:
1 x FTD232RL

2 x PC457L0NIP0F (the opto isolator)

1 x Hirose UX60-MB-5ST usb connector

FB1 is a Ferrite Bead in an 0805 package

Everything below this is a 1206 package

C1 is a 0.01uF cap

C2 and C3 are 47pF caps

C4 is a 0.1uF cap

R1 and R2 are 270 ohm resistors

R13 and R14 are 4.7k ohm resistors

R15 and R16 are 220 ohm resistors (for 5V i/o voltages)

TXLED and RXLED can be any 1206 chipled.  You should change your R1 and R2 based on the max forward voltage of the LED you choose!