If they are 8mm or Hi8, the best thing to do is find a Digital8 camera which will play them back. It digitizes in-cam and outputs through the firewire. However, not all Digital8 cameras are reverse compatible, which I found out the hard way.
Since my original Digital8 started eating tapes and my replacement doesn't play Hi8s I have been running them out the audio RCAs and video-S of a Hi8 cam through my PD170 which digitizes and outputs through firewire.