This is really great board: AVR Ethernet I/O board with 2x RS232, 2x USB connector, BW composite video, Real Time Clock with battery backup, PS/2 keyboard connector, Wiz810MJ ethernet module and LCD 16x2 display.

Photo: Ben Zijlstra

An USB-to-Serial (I2C/SPI/GPIO) bridge.

The Bus Pirate is a universal bus interface that talks to most chips from a PC serial terminal, eliminating a ton of early prototyping effort when working with new or unknown chips. Now with USB capabilities in the version 2.

An open source interpreted language shell for the Arduino serial port.

A smart and small solution to connecting your devices with PC via USB.

Microchip Technology Inc.announced a family of 8- and 32-Kbyte stand-alone serial SRAM devices, which increase a system’s available RAM memory by adding small, inexpensive external devices.

The PICkit Serial Analyzer is a low-cost USB-based tool used to direct communication between a PC and an external serial device.

This small realization, based on one of the most common IC (MAX232) is designed to create a small and convenient TTL to RS232 and vice versa convertor.

This EEPROM programmer reads, writes and erases I²C 24C EEPROM devices through a PC serial port (RS-232) interface.

Terminal with ATmega8, RS232 interface and TV out by Vasilis Serasidis.