well sempron and celeron are at the bottom of the spectrum for both amd and intel. centrino (pentium m) were the processors before the core duo came out. then there is core duo for laptops, and then core 2 duo. that should be in order of performance, although you could get a core duo to outperform a core 2 duo.
that is from pentium, im not as sure with amd, but generally sempron at the bottom, then turion is the single core, and there is probably a dual core version now