Why does this make you hate Intel? Yes, the P4 was probably a rather limited processor from the get-go, but other manufacturers have had limited-growth processors as well. It's cool to see a Pentium M beat out a P4 clocked more than 1gHz more than the P-M -- goes to show that CPU performance is far more than clockspeed. At any rate, Intel makes the P-M, and it's an excellent processor. The dual-core Yonah mobile processor is likely to be out the first half of 2006, though perhaps the official release announcement of this processor will cause a price-drop in the Pentium M line. I think NewEgg and ZipZoomFly have the least expensive P-M (1.7ghz) for somewhere aroudn $180-$210 -- a bit pricey for most folks' carputers.
The P-M is an excellent choice for carputers though, mainly because of its very high performance, excellent mobo/component support, and extremely low power consumption given the clock speed. I think most P-Ms are designed to consume less than 25-30 watts, which is awesome considering >2ghz clock speeds.