USB-Serial Convertors

Sparkfun FTDI Breakout Board:

This is the one to use for programming the Ardweeny, the female headers go in directly to the programming headers on the ardweeny, and they can only go in one way (the header toward the center of the Ardweeny, and the chip and the mini usb toward the edge of the Ardweeny.

Comes 5V by default. if the trace on the back between 5V and center is cut, and the 3.3V pad to center is bridged, then it becomes 3.3V. (Wish there was a jumper here, bridging and desoldering more than a couple of times pulls the pads off the board!)

Sparkfun page for this product.

SuperDroids USB to TTL Converter:

This USB to TTL converter provides two way serial communications signal conversion between the TTL (Transistor Transistor Logic) input/output (from a TTL device such as a PIC) to and from a personal computer via virtual COM port. The USB cable installs into your PCs USB port and installs as a COM port. Virtual COM port (VCP) drivers cause the USB device to appear as an additional COM port available to the PC. Application software can access the USB device in the same way as it would access a standard COM port. This is ideal for connecting your TTL microcontroller serial communications to the PC. Today’s computers typically do not have RS232 ports on them anymore, this solves that issue by providing you a virtual COM port using the common USB port. This is just a bare board with no housing, you can solder you own cable onto the board and connect it to your TTL device.

Easy to install. The drivers can also be downloaded from the FTDI site. http://www.ftdichip.com/Drivers/VCP.htm For first time installs it will install 2 drivers before its ready to operate. You should only need to do this once per PC. Once installed you can remove and reinsert the cable without having to install the drivers each time. Goto to your device manager to determine what COM port was used. Its typically the next available COM port on your PC.

This is the same board we use in our USB to TTL cables. Follow this link for a schematic and more detail on the cable.

1 - Rx -TTL from PC
2 - Tx - TTL to PC
3 - Ready to Send
4 - Clear to Send
5 - ground
6 - +5 volts output (250mA max)

USB to TTL Converter - Bare Board, (Item #:MCU-036-000), $11.50
Got this from SuperDroids.

Sparkfun FT232RL Breakout Board:

Board should be 3.3V by default. If the solderpad is cleared, then it becomes 5V. or if you want any other voltage (like 1.8V) then connect that voltage to VCCIO.
(i cleared the solder pad on the one i have)

Got this from Sparkfun.

USB AD43 SYSCONE Serial 4 COM port adapter:

The universal adapter USB-AD43 allows your PC to communicate with Dynamixel / Bioloid bus devices (AX-12, AX-S1, IMU, etc), provides 4 serial(COM) ports with TTL levels(0-5V), I2C standard interface, SPI interface, JTAG interface, an Enhanced Bit-Bang Mode interface and a Pony Programmer adapter (the famous memory / microcontroler programmer...

Got this from Wright Hobbies.

FTDI Friend:

The FTDI Friend is a tweaked out FTDI FT232RL chip adapter. Sure, like the well-known FTDI cable, it can provide power to your project and there are 4 signal lines for sending data back and forth. But the Friend can do much more! For example, you can change the signal and power lines to be either 3.3V or 5V. Arduino-derivatives and XBees use the RTS line for programming but what if you need that DTR line? Its there for you. By default, we've set it up so that it matches our FTDI cables. The 6th pin is RTS (as of Arduino IDE v18 this will work perfectly for uploading to 'inos), the power wire is +5V and the signal levels are 3.3V (they are 5V compliant, and should work in the vast majority of 3.3V and 5V signal systems)...

Got this from Adafruit.

PL2303 Mini USB UART Board:

The PL2303 USB UART Board (mini) is an accessory board that features a USB-to-UART serial convert PL2303, USB mini connector and 3-LED: TXD LED, RXD LED, POWER LED; Also a jumper used for selecting VCC output level provided on the board.
Got this from dealextreme.