The Intel Celeron family has many members roaming the entry level segment of the market. The Celeron E series with its 45nm technology are the latest to arrive. Clock frequencies start at 2.0GHz and goes up to 2.5GHz with the flagship, but with some overclocking you can go higher, a lot higher as it turns out. at Inpai.com they have published screenshots of a Celeron E3200 processor overclocked to 4.4GHz with just air cooling.
That a processor costing just $40 and operate at 2.4GHz can be pushed over 4GHz with simple air cooling is the least to say impressive. The processor required 1.360V operating voltage to reach 4.4GHz where it passed and completed both Cinebench and SuperPi 1M.