More generic drive caddy at a bit less than half the price of the MCETech one ($42): http://newmodeus.com/shop/index.php?main_page=product_info&products_id=220

The MCETech does currently come with a free USB enclosure to relocate your optical drive.

If you're OK with a bunch of wires and tape holding an SSD in place, you can actually just make a cable for around $10: http://forums.macrumors.com/showthread.php?t=680228

I've been meaning to do this mod since I bought my unibody MBP 17", just haven't had the opportunity to commit to it yet - mainly due to some disappointment with SSDs available.