Rob,
These days I am really loving a sauce developed by Amy Anderson of the Ranch House BBQ restaurant and competition team. It's published in "Weber's Charcoal Grilling," along with her baby back rib recipe. It is a ketchup-based sauce with a great balance of cider vinegar, Worcestershire sauce, molasses, and a few other ingredinets. Obviously, Amy likes it on ribs, but I've used it on chicken and steak, too. I hope you try it.
Thanks,
Jamie