To make a long story short, celerons are junk and are essentially failed pentiums and core 2 duo's;don't ever get a computer with one. Centrinos in a modern sense are core 2 duos that are made specifically for laptops, i.e. lower clock speeds, higher thermal variation tolerance, etc... Unlike the other two, Athlons are made by AMD and I believe they are in their second generation. I believe some, usually the 2 core variants are found in laptops, while the others are mostly for desktops.
If you are in the market for a laptop, either go with an Athlon II or a Centrino based cpu.