Intel released the Pentium 4 at the end of 2000. Using RDRam it was an expensive solution that most of the market did not need. Lots of MegaHertz and lots of $'s. Since then, chipsets that support SDRAM and the current DDR RAM have made it a worthwhile proposition. The P4's clock speed has increased to the magic 3GHz for this Christmas, although for most uses lower speeds are more than adequate.
AMD's AthlonXP range continues to be worth serious consideration, as does the Duron range which is widely acknowledged to have better "oomph" per $ than the P3 based Celerons (the faster Celerons are based on the P4 core).
Cyrix's current owner (Via) continues the name with the C3 at the price conscious end of the market.
Transmeta, a recent low power device, has started to make inroads into PDA's. This will allow a viable way to increase battery life since no new battery technologies have shown any signs of emerging.
As usual, all this means more choice and more MHz for your money if that's what you want, or less money for the same power.