An awesome little USB to 5V serial connector based around the FTDI FT232RL chip.
This version includes a reset output triggered by the DTR line and an activity output.
This is a complete kit which includes 6 surface mount passives, the surface mount FT232RL chip, a through-hole USB-B connector, and the PCB.
For more indepth information, see the original blog post (note, it doesn't describe the two extra pins added for reset.