ThinkPad

alphabetical order

 * 300 series (replaced by A series): CPUs from 386SL/25 to Pentium III 450; larger, heavier, slower, and cheaper (Parts: Impact)
 * 390X: Mobile Pentium II / 400, 6.4GB, 15" 1024x768 active matrix TFT
 * 500 series (replaced by X series): CPUs from 486SX2-50 Blue Lightning to Pentium III 500: main line; lightweight, slim, only HD onboard
 * 600 series (replaced by T series): Pentium MMX, II, and III; very durable
 * 700 series (replaced by A & T series): cutting-edge models – largest screens, largest HDs, fastest CPUs (for the time)
 * 700: monochrome screen
 * 700C: active matrix TFT color screen
 * 701 models have the "butterfly" fold-out keyboard
 * 800 series: PowerPC 603e CPU at 100 MHz (except where noted); SCSI2 instead of IDE
 * 860: CPU at 160 MHz
 * A series
 * Hardware Maintenance Manual
 * A31p: as of 2006 (presumably), seven of these are being used in orbit aboard the International Space Station
 * R series
 * R30: manufactured by Lenovo
 * R31: manufactured by Lenovo
 * R32: ThinkWiki
 * R40e: manufactured by Lenovo
 * T series
 * T20 series (T20, T21, T22, T23): Pentium III Mobile, 650 MHz to 1+ GHz
 * T23: internal WiFi
 * T30 series (one model only): Intel Mobile Pentium 4 from 1.6 GHz to 2.4 GHz
 * T40 series (T40, T41, T42, T43): Intel Pentium M Processor 1.3 GHz to Pentium M 770 at 2.13 GHz
 * T60 series
 * X series
 * X20 series
 * X30 series
 * X40 series: very well-supported by OpenBSD
 * X41 tablet model
 * X60 series
 * Z series (introduced by Lenovo)
 * Z60 (Z60, Z61)

chronological order

 * "ThinkPad", no model number: tablet computer without keyboard, using Go PenPoint OS
 * models 700 / 700C : first ThinkPads introduced

Reference

 * ThinkWiki
 * ThinkWiki