Hi Nicole - this re-post is for you. :)
I made my first crochet hook handle in 2002 - I needed more substance to hold in my hand - I was having a problem with having to stop crocheting and stretch out my fingers every once in a while. I thought of tape but I didn't think that that would feel comfortable or look very nice. My next thought was polymer clay. I had a small stash of it leftover from trying to make beads, so I tried it and it worked great.
This is how I create my crochet hook handles:
Step 1: knead the polymer clay to make it more pliable. (by the way, I use Sculpey and Fimo polymer clays)
Step 2: wrap the polymer clay around your crochet hook handle and shape it to your preference. I roll the handle on my dining room table to help smooth it out.
Step 3: bake in a toaster oven at 275* for 15 minutes per 1/4" thickness.
Once you get the gist of creating these handles, you can let your imagination go. My favorite style is swirling 2 or 3 colors together with a glass bead on top. I think they're pretty and they really help out my crocheting hand. :)
***Edited to add a couple of tips:
1. use only metal crochet hooks. I tried a plastic hook once and it drooped down.
2. lay the polymer clay hook on a soft bed of quilt batting.
3. fashion a little tent out of aluminum foil to cover the hook and quilt batting while baking.