All of the ATtiny’s are basically the same apart from the number of actual IO pins and a few specific features.

ATtiny24 / ATtiny44 / ATtiny84

14pin
Internal osc +-10% without user calibration (ATtiny841 is drop in replacement with better accuracy)

ATtiny85

8 pin

ATtiny441 / ATtiny841

14 pin
Internal osc +-2% without user calibration

Default pin numbering to use: Counterclockwise

// ATMEL ATTINY84 ARDUINO PIN NUMBERS - "COUNTERCLOCKWISE" PIN MAPPING OPTION
//                    +-\/-+
// [VCC]        VCC  1|    |14  GND        [GND]
//        _0_   PB0  2|    |13  AREF  _10_  
//        _1_   PB1  3|    |12  PA1   _9_   
// [RST]        PB3  4|    |11  PA2   _8_   
//        _2_   PB2  5|    |10  PA3   _7_   
//        _3_   PA7  6|    |9   PA4   _6_  [SCK]
// [MOSI] _4_   PA6  7|    |8   PA5   _5_  [MISO]
//                    +----+
// [Programmer pins in brackets]

So, if you have a LED connected to pin 11, you’d declare it as this:

#define IO_LED              8   //PA2

UART pins for serial programming

(UART0 default pins):

4 – PB3, RESET
11 – PA2, RXD0
12 – PA1, TXD0

Analog pins

Example:

PB0 is accessed using analogRead(A11)

ATtiny861

20 pin