Intel Celeron 433

Conclusion

Your best bet with the Celeron has been, and always will be, a 300A that is guaranteed overclockable (by the vendor you're buying from) to 450MHz.   There are still quite a few vendors online that do offer this guarantee, and for the money you'll end up spending on a 300A, the boost to 450MHz is like getting something for nothing.  But what happens when the 300A is no longer an option?  Then things get a bit messy.

The one processor you definitely want to stay away from is the Celeron 333, whose overclocking potential is next to nothing in comparison to the rest of the processors.  The 333 will give you the bare minimum, and realistically, won't overclock too far beyond the 400MHz limit.  The processor to keep an eye on is the Celeron 366.  The reason being is this, the price of the 366 at the time of publication was at the Celery sweet spot, around $100, and the overclocking potential of the CPU is wonderful.  If your system can work fine at the 83MHz FSB, then the 366 will almost definitely crank out 458MHz worth of power, and even in the rare case that the 83MHz FSB  isn't an option, the 75MHz FSB will give you the 413MHz clock speed which isn't all that much slower in comparison to 458MHz. 

In the future, once the price drops a bit, the Celeron 433 will be the processor to hunt after.  You'll probably want to skip the Celeron 400 altogether as its overclocking potential isn't that great, however the 433, with its 6.5x clock multiplier, would make an excellent couple with the 75MHz FSB for a clock speed definitely faster than any officially rated Pentium II processor.

So for the time being, the processor to get is the Celeron 366, however in the future, the Celeron 433 will rise to take the 366's place, and the cycle will continue.  And that, my friend, is the way it is.