Ok, one slice of humble pie for me, please. I do know a *little* bit about cars, I'm no master mechanic by any means, but I should have known this much...

It was the negative battery cable. I pulled the thing off and looked at it under better light and it was corroded to all get out. So I went to the local AutoZone, picked up a $10 replacement and slapped it on, and the car started up like it was p***ed off at me! I'm going to leave that new starter in. The old one was pretty gunked up with clutch dust, so I figure it doesn't hurt to have a new one to go with the new clutch, even though it was probably an unnecessary replacement.

Thanks for the help, guys, I should have figured this one out on my own, but I'm glad you guys were here when I was being too dumb to brain