Well, I managed with an audio Y-cable; one end into the headphone jack on my boombox, the other into the left/right plugs on the back of my PowerMac. That and a handy little program called SoundMaker 1.0.3 from MicroMat. Opened up SoundMaker, stuck the tape in, pushed play and off I went. There was a slight bit of 'tape noise', but SoundMaker took care of that.
I'm sure I'll get better with practice, but the first experience was fairly painless. The resulting MP3 file is here. Not perfect, but I've heard worse...
Though, truth to tell, for the amount of tape that y'all want to transfer to digital, I'm thinking there must be a better way. I'd be interested in hearing it myself.
= )