What are you driving? Why do you need amplification? Do you need to drive a higher current load, or a higher voltage load, or both?
Personally, I use BS170 MOSFETs as low-end drivers unless there's a real reason to do anything else. Note that these do not "amplify" in the "multiplication" sense -- instead, they go "on" when the digital control pin is "ON," and vice versa, which matches what you want for a PWM signal.