What's the Android equivalent of /etc/fstab? Sometimes I really wish they hadn't messed around with Linux so much! I know there's an /etc/fstab in there somewhere, but where? 

I'd like to mount some partitions with alternative filesystems (because I don't like FAT32).
Don't think about Android as a heavily modified Linux distribution. Because it's not. The nearly only thing that Android shares with a Linux distribution is the kernel. And even this component is modified. Also other core components, like the libc, differ.

Android has no /etc/fstab

You don't need /etc/fstab to mount an partition. But there is IIRC no mount command either.dev_mount should work (root required). To answer your questions title: All startup system mounting is done with the/etc/vold.fstab helper script.