Ok, when I installed Slackware 9.1 onto my 4GB harddrive (I know, it's small) here's how I set up the partitions:

2.5 GB - root; hdd1
1 GB - home; hdd2
0.5 GB - swap

I noticed after a few days that Slack setup didn't make home on hdd2, it put it on hdd1. Also my etc/fstab has no mention of hdd2. My swap space is working properly.

Is there any way I can move my /home directories to hdd2, or do I have to re-install (not a big deal since I don't have much installed...this is a learning disk, not for actual work, yet).

sounds like a screw up on your part during the installation partition phase ...

anyways before we attempt the steps of rearranging everything, post the output of :
fdisk -l
you will have to be root to do this ....

but just for your knowledge you will have to have that free space allocated it, and change your fstab to point to the new /home and then re-mount it to its new location ..
but if you did in fact screw in the partitioning, then technically you shouldn't have free space and it should all be on / as 3.5GB ... and in that case you will have to either resize the partition , or like you said start over and re-install

I know I didn't screw up the making of the partitions (I checked them three times before and after I wrote the table).

Where I think I may have screwed up is during the Slack setup when slack asks what partition to use for root. I didn't notice it asking what partition to use for home.

I'll post the output of fdisk -l tonight when I get home.