This page contains all the power levels that have been shown so far. These may not be 100% accurate, but are very close.
The Radditz Saga
Radditz - 1,200
Piccolo - 408
Piccolo w/ Special Beam Cannon (1st Try) - 1,330
Piccolo w/ Special Beam Cannon (2nd Try) - 1,440
Goku - 416
Gohan - varies from 1 to 1,370 (it changes with his emotions)
The Vegeta Saga
Yamcha - 1,065
Krillin - 1,673
Tienshinhan (Tien) - 1,834
Piccolo - 2,500
Piccolo (when most powered up) - 3,400
Gohan - 2,000
Goku - 5,000
when powered up - 8,000+
Kaioken x1 - 12,000
Kaioken x2 - 16,000
Kaioken x3 - 24,000
Kaioken x4 w/ Kamehameha - 45,000
Nappa - 4,000
Vegeta - 8,000
The Freeza Saga Kui - 18,000
Dudoria - 21,000
Vegeta - 22,000
Zarbon - 22,000
Krillin (after Guru power up) - 13,000
Gohan (after Guru power up) - 22,000
Vegeta (healed after first fight w/ Zarbon) - 30,000
Zarbon (transformed) - 26,000
Guldo - 10,000
Jeise - 29,000
Burter - 31,000
Recoome - 33,000
Goku (while fighting Ginyu) - 180,000
Captain Ginyu - 120,000
Vegeta (after Ginyu force) - 200,000
Goku (after Ginyu force) - 550,000
Freeza (form 1) - 530,000
Freeza (form 2) - 700,000
Freeza (form 3) - 870,000
Freeza (form 4) - 1,200,000
Nail - 42,000
Nail (mega charge up while fighting Freeza) - 200,000
Piccolo - 400,000
Piccolo (without weighted clothing) - 440,000
Piccolo (merged w/ Nail) - 800,000
Goku (max power) - 870,000
SuperSaiyan Goku - 1,500,000