Celeron D is a Prescott core Celeron, and has 256k cache with a 533MHz FSB. It is a lot better than the Northwood Celeron, probably because of the Prescott's improved branch predictor. Here is some benchmarks, as you can see they even give Athlon XP 2800+'s a run for their money. Overclocking beasts too:
http://www.xbitlabs.com/articles/cpu...celeron-d.html