Pin	Description
1+	Positive 1
1-	Negative 1
2+	Positive 2
2-	Negative 2

Mini-DIN 4-pin

S-Video

Pin	Description
1	Ground (Y)
2	Ground (C)
3	Luminance (Y)
4	Chrominance (C)

Apple Desktop Bus

Pin	Description
1	ADB bidirectional data
2	Power switch
3	Power +5V
4	Ground

DIN 5-pin

Unbalanced Audio

Pin	Description
1	Signal Input (Left channel)
2	Ground
3	Signal Output (Left channel)
4	Signal Input (Right channel)
5	Signal Output (Right channel)

MIDI

Pin	Description
1	Not connected
2	Shield (input)/Ground (output)
3	Not connected
4	Signal (source on input, sink on output)
5	Signal (sink on input, source on output)

Mini-DIN 6-pin

PS/2

Pin	Description
1	Key data (keyboard), Button/Position data (mouse)
2	not connected
3	Ground
4	Power, +5V
5	Clock
6	not connected

DIN 7-pin

Image credit to captain18 at LiveJournal

SATA

Pin	Description
1	Ground
2	Transmit+ (data)
3	Transmit- (data)
4	Ground
5	Receive+ (data)
6	Receive- (data)
7	Ground

eSATA

Pin	Description
1	Ground
2	Transmit+ (data)
3	Transmit- (data)
4	Ground
5	Receive+ (data)
6	Receive- (data)
7	Ground

8-pin EIAJ

Image credit to Lab Guy's World

Pin	Description
1	Audio out
2	Video out
3	Video in
4	Video in
5	Audio out
6	Video out
7	Audio in
8	Audio in

Mini-DIN 8-pin

Apple RS-422

Pin	Description
1	Output Handshake
2	Input Handshake or External Clock
3	Transmit- (data)
4	Ground
5	Receive data- (data)
6	Transmit data+ (data)
7	General Purpose Input
8	Receive data- (data)

DE-9

RS-232

Pin	Description
1	Carrier detect
2	Receive data
3	Transmit data
4	Data terminal ready
5	Ground
6	Data set ready
7	Request to send
8	Clear to send
9	Ring indicator

Sony 9-pin RS-422 VTR protocol

Pin	Description
1	Frame ground
2	Transmit A
3	Receive B
4	Receive common
5	spare/ground
6	Transmit common
7	Transmit B
8	Receive A
9	Frame ground

Mini-VGA

Pin	VGA input	Video output
1	Ground	Ground
2	Vertical Sync	not used
3	Horizontal Sync	not used
4	Red return	Ground
5	Red video	S-Video Chroma (C)
6	Green return	Ground
7	Green video	S-Video Luma (Y)
8	Power +5V	Power +5V
9	Blue video	Composite video
10	DDC data	DDC data
11	DDC clock	DDC clock
12	Ground
13	Cable detect	Cable detect
14	Blue return	Ground

DA-15

Joystick Connector

Pin	Signal name	Description
1	+5v	Power
2	A Right Button	Joystick/A Right Button
3	A / X-position	Joystick/A X-Coordinate
4	Signal GND	Ground
5	Signal GND	Ground
6	A / Y-position	Joystick/A Y-Coordinate
7	A Left Button	Joystick/A Left Button
8	+5v	Power
9	+5v	Power
10	B Right Button	Joystick/B Right Button
11	B / X-position	Joystick/B X-Coordinate
12	MIDI Out	MIDI Output
13	B / Y-position	Joystick/B Y-Coordinate
14	B Left Button	Joystick/B Left Button
15	MIDI In	MIDI Input

DA-15 had highly varied pinouts depending on the specific peripheral in question. See this webpage/a> for more options.

DE-15

VGA

Pin	Description
1	Red video
2	Green video
3	Blue video
4	reserved
5	Ground
6	Red ground
7	Green ground
8	Blue ground
9	Key (no pin)/Optional +5V power output
10	Sync ground
11	Monitor ID Bit 0 (optional)
12	I2C bidirectional data
13	Horizontal Sync
14	Vertical Sync
15	I2C data clock

USB

USB 2.0

Pin	Type A/Type B	Mini-A/Mini-B	Micro-A/Micro-B
1	Power +5V	Power +5V	Power +5V
2	Data -	Data -	Data -
3	Data +	Data +	Data +
4	Ground	Ground/Attached device indicator/not connected	Ground/attached device indicator/ground
5		Ground	Ground

USB 3.0

Pin	Type A	Type B	Powered B	Micro-B
1	Power +5V	Power +5V	Power +5V	Power +5V
2	Data - (2.0 speed)	Data - (2.0 speed)	Data - (2.0 speed)	Data - (2.0 speed)
3	Data + (2.0 speed)	Data + (2.0 speed)	Data + (2.0 speed)	Data + (2.0 speed)
4	Ground (power)	Ground (power)	Ground (power)	ID configuration line
5	RX- (Superspeed receiver)	TX-	TX-	Ground
6	RX+ (Superspeed receiver)	TX+	TX+	TX-
7	Ground (signal)	Ground (signal)	Ground (signal)	TX+
8	TX- (Superspeed transmitter)	RX-	RX-	Ground
9	TX+ (Superspeed transmitter)	RX+	RX+	RX-
10			Power provided by device	RX+
11			Ground for power provided by device

USB 3.1

Pin	Type C
A1	Ground
A2	TX1+ (Superspeed transmitter)
A3	TX1- (Superspeed transmitter)
A4	Power
A5	CC1 (orientation configuration information)
A6	Data+ (2.0 speed)
A7	Data- (2.0 speed)
A8	Secondary bus 1
A9	Power
A10	RX2- (Superspeed receiver)
A11	RX2+ (Superspeed receiver)
A12	Ground
B1	Ground
B2	TX2+ (Superspeed transmitter)
B3	TX2- (Superspeed transmitter)
B4	Power
B5	CC2 (orientation configuration information)
B6	Data+ (2.0 speed)
B7	Data- (2.0 speed)
B8	Secondary bus 2
B9	power
B10	RX1- (Superspeed receiver)
B11	RX1+ (Superspeed receiver)
B12	Ground

FireWire

4-pin

Pin	Description
1	Twisted-Pair B- (data)
2	Twisted-Pair B+ (data)
3	Twisted-Pair A- (data)
4	Twisted-Pair A+ (data)

6-pin

Pin	Description
1	Power
2	Ground
3	Twisted-Pair B- (data)
4	Twisted-Pair B+ (data)
5	Twisted-Pair A- (data)
6	Twisted-Pair A+ (data)

9-pin

Pin	Description
1	Twisted-Pair B- (data)
2	Twisted-Pair B+ (data)
3	Twisted-Pair A- (data)
4	Twisted-Pair A+ (data)
5	A shield
6	Ground
7	not used
8	Power
9	B shield

Mini-DVI

Pin	Description
1	Data 2+
2	Data 2-
3	Data 1 +
4	Data 1 -
5	Data 0 +
6	Data 0 -
7	Clock +
8	Clock -
9, 10, 11, 12, 13, 14, 15, 16	Digital Signal Ground
17	Power +5V
18	DCC data
19	not used
20	Analog Blue
22	Analog Green
21, 23	not used
24	Analog Red
25	Detect
26	DCC clock
27	not used
28, 30, 32	Digital Signal Ground
29	Analog Horizontal Sync
31	Analog Vertical Sync

DVI

Pin	Description
1	Data 2-
2	Data 2+
3	Data 2/4 shield
4	Data 4-
5	Data 4+
6	DDC clock
7	DDC data
8	Analog Vertical Sync
9	Data 1-
10	Data 1+
11	Data 1/3 shield
12	Data 3-
13	Data 3+
14	Power +5V
15	Ground
16	Detect
17	Data 0-
18	Data 0+
19	Data 0/5 shield
20	Data 5-
21	Data 5+
22	Clock shield
23	Clock +
24	Clock -
C1	Analog Red
C2	Analog Green
C3	Analog Blue
C4	Analog Horizontal Sync
C5	Analog Ground

DisplayPort

Pin	DisplayPort (Full)	Mini DisplayPort
1	Main Lane 0+ (data)	Ground
2	Ground	Detect
3	Main Lane 0- (data)	Main Lane 0- (data)
4	Main Lane 1+ (data)	Ground
5	Ground	Main Lane 0+ (data)
6	Main Lane 1- (data)	Ground
7	Main Lane 2+ (data)	Ground
8	Ground	Ground
9	Main Lane 2- (data)	Main Lane 1+ (data)
10	Main Lane 3+ (data)	Main Lane 3+ (data)
11	Ground	Main Lane 1- (data)
12	Main Lane 3- (data)	Main Lane 3- (data)
13	Ground	Ground
14	Ground	Ground
15	Auxiliary Channel +	Main Lane 2+ (data)
16	Ground	Auxiliary Channel +
17	Auxiliary Channel -	Main Lane 2- (data)
18	Detect	Auxiliary Channel -
19	Return for Power	Ground
20	Power	Power

HDMI

Pin	Type A (Full)	Type C (Mini)	Type D (Micro)
1	Data2 +	Data2 shield	detect
2	Data2 shield	Data2 +	not connected
3	Data2 -	Data2 -	Data2 +
4	Data1 +	Data1 shield	Data2 shield
5	Data1 shield	Data1 +	Data2 -
6	Data1 -	Data1 -	Data1 +
7	Data0 +	Data0 shield	Data1 shield
8	Data0 shield	Data0 +	Data1 -
9	Data0 -	Data0 -	Data0 +
10	Clock +	Clock shield	Data0 shield
11	Clock shield	Clock +	Data0 -
12	Clock -	Clock -	Clock +
13	control	DDC ground	Clock shield
14	not connected	control	Clock -
15	DDC clock	DDC clock	control
16	DDC data	DDC data	DDC ground
17	DDC ground	HEC+/not connected	DDC clock
18	Power +5V	Power +5V	DDC data
19	detect	HEC-/not connected	Power +5V

SCART

Pin	Description
1	Audio Out right
2	Audio In right
3	Audio Out left (+ Mono)
4	Audio Ground
5	RGB Blue ground
6	Audio In left (+ Mono)
7	RGB Blue in
8	Switch control (Audio/RGB)
9	RGB Green ground
10	Clockpulse out
11	RGB Green in
12	Data out
13	RGB Red ground
14	Data ground
15	RGB Red in/S-Video Chroma (C)
16	Blanking signal
17	Composite Video ground or S-Video Luma ground
18	Blanking signal ground
19	Composite video out
20	Composite video in / S-Video Luma / RGB Sync
21	Ground/shield (chassis)

DB-25

Parallel SCSI

Pin	Description
1	Request
2	Message
3	Input/Output
4	Reset
5	Acknowledge
6	Busy
7	not used
8	Data Bus 0
9	not used
10	Data Bus 3
11	Data Bus 5
12	Data Bus 6
13	Data Bus 7
14	not used
15	Control
16	not used
17	Attention
18	not used
19	Select
20	Data Parity
21	Data Bus 1
22	Data Bus 2
23	Data Bus 4
24	not used
25	Termination Power

Parallel/Printer Port

Pin	Description
1	Strobe
2	Data Bit 0
3	Data Bit 1
4	Data Bit 2
5	Data Bit 3
6	Data Bit 4
7	Data Bit 5
8	Data Bit 6
9	Data Bit 7
10	Acknowledge
11	Busy
12	Paper Out
13	Select
14	Autofeed
15	Error
16	Reset
17	Select
18	Signal Ground
19	Signal Ground
20	Signal Ground
21	Signal Ground
22	Signal Ground
23	Signal Ground
24	Signal Ground
25	Signal Ground

Serial RS-232 Devices

RS-232 serial device pinouts could vary wildly depending on the specific device in question. Consult this webpage for examples.