The latest Intel celeron's are actually very good for a budget processor. Using the PIII core instead of the older celeron's PII core, the processor performs pretty much the same as the PIII. Slightly slower due to less L2 cache, 128Kb instead of 256Kb.
This processor's greatest point however is that (motherboard and memory permitting) you can over clock them by a long way! The best i have found is the PIII cored Celeron 1GHz which will clock by 150% to 1.5GHz! No bullsh*t, it will do it if you use a large fan and 150MHz RAM. The normal celerons run so far under their potential that a fan is not even a necessity on a non clocked one.
In game performance is good, my celeron 1GHz running at 1.2GHz with a GeForce 2 will return a little over 5000 3DMark 2000 points, not bad for a "budget" processor. A recent magazine article actually found that the celeron had better game performance than the more expensive PIII clock for clock, weird.