Microcontrollers are nothing without any input devices (like sensors) or output devices (like displays, LEDs, servos, ...).
Simple Input/Output
Simple Analog Sensors
Pot3
Simple input device - 3 potentiometers
Simple input device - 3 potentiometers
Accelerometer
Connecting a 2/3 axis accelerometer
Connecting a 2/3 axis accelerometer
TEMT6000
Ambient Light Sensor
Ambient Light Sensor
TMP36
Temperature Sensor
Temperature Sensor
Simple Output
LED
Relay
Protocols
I2C
I2C
Overview
Overview
WiiChuck
Wii Controller Connector
Wii Controller Connector
DS1307 & DS3231
Real Time Clock (RTC)
Real Time Clock (RTC)
24xx256
I2C EEPROM 256kbit
I2C EEPROM 256kbit
HMC6352
Digital Compass
Digital Compass
BMP085
Digital Pressure Sensor
Digital Pressure Sensor
SPI
SPI
Overview
Overview
74HC595
8-Bit Serial-In, Parallel-Out Shift Register
8-Bit Serial-In, Parallel-Out Shift Register
74HC165
8-Bit Parallel-In, Serial-Out Shift Register
8-Bit Parallel-In, Serial-Out Shift Register
TLC5925
16-Channel Constant-Current LED Driver
16-Channel Constant-Current LED Driver
TLC5940
16-Channel PWM LED Driver
16-Channel PWM LED Driver
UART
UART
Overview
Overview
FTDI
USB Serial Converter
USB Serial Converter
GPS
LS20031 GPS-Bee
LS20031 GPS-Bee
ELM327
on-board diagnostics interface
on-board diagnostics interface
ID-12
RFID
RFID
1-Wire
1-Wire
Overview
Overview
DS1820, DS18B20, DS18S20
Temperature Sensor
Temperature Sensor
DS2450
Quad A/D Converter
Quad A/D Converter
DS2413
Dual Channel Addressable Switch
Dual Channel Addressable Switch
DS2408
8 Channel Addressable Switch
8 Channel Addressable Switch
DS2480
Serial to 1-Wire Line Driver
Serial to 1-Wire Line Driver
MIDI
MIDI
Overview
Overview
MeeBlip
The Hackable Digital Synth
The Hackable Digital Synth
MCP4921
MidiVox Shield
MidiVox Shield
VS1053
Musical Instrument Shield
Musical Instrument Shield
ATSAM2195
Fluxamasynth Shield
Fluxamasynth Shield
YM2149
YM_MINI Synthesizer
YM_MINI Synthesizer
Piezo
YM_MINI Synthesizer
YM_MINI Synthesizer
LCD
HD44780 LCD
16/20 × 1/2/4
16/20 × 1/2/4
KS0107 LCD
128 × 64
128 × 64
PCD8544 (Nokia 3310 & 5110 LCD)
84 × 48
84 × 48
Zigbee / 802.15.4
Zigbee / 802.15.4
XBee
XBee
Funnel
Arduino Fio
Arduino Fio
ConnectPort X2
XBee / Ethernet Gateway, XIG
XBee / Ethernet Gateway, XIG
Wireless Local Area Network / 802.11
Roving Networks' WiFly GSX 802.11b/g
WiFly Shield
WiFly Shield
Servos & Motors
Servo Moters
Other Protocols
Ping
Ultrasonic Distance Sensor
Ultrasonic Distance Sensor
Touch Screen
4-Wire Resistive Touch Technology
4-Wire Resistive Touch Technology
Pulse Sensor
Optical Heart Rate Pulse Sensor
Optical Heart Rate Pulse Sensor
SHT1x
Humidity and Temperature Sensor
Humidity and Temperature Sensor
Microcontrollers
AVR
AVR
ATtiny & ATmega
ATtiny & ATmega
AVR Programmer
ATtiny2313 & ATtinyX5
ATtiny2313 & ATtinyX5
ATmegaX8 (Arduino)
ATmega88 ATmega168 ATmega328
ATmega88 ATmega168 ATmega328
ATmegaX4
ATmega164 ATmega324 ATmega644
ATmega164 ATmega324 ATmega644
ATtinyX5
ATtiny25 ATtiny45 ATtiny85 (ATtiny13)
ATtiny25 ATtiny45 ATtiny85 (ATtiny13)
ATtiny2313
Arduino Shields (Daughterboards)
SpeakJet / TTS256
Voice and Sound Synthesizer
Voice and Sound Synthesizer
Useful Prototyping / Debugging / Reverse Engineering Tools
Logic Analyzer
Poor Man's Logic Analyzer
Open Workbench Logic Sniffer
Saleae Logic Analyzer
Oscilloscope
Poor Man's Oscilloscope
Other
Bus Pirate
USB Infrared Toy
Data Logger
AVR Stick, uLog
AVR Stick, uLog
References
What connectors to use?
Resistor Values
Batteries
Radio Control (R/C or RC)