I'm not sure how many people, if anyone, might be interested in this, but I figured I'd pass it on just in case.
It seems that IBM has a special thing going on right now. You can take an online assessment exam over some of their DB2 certifications, and if you score a 75% or greater, you get a voucher to take the certification test for free (Normally costs over $100 each).
After a quick glance at it, I'm not entirely sure if you can manage to get just the final test required for certification free, or all of them. If you could manage to get all required tests for a certification free, though, that'd be pretty sweet. ;-)
Details are at their website, here.