The only one i know for sure that would work is a T3400, but that's not much of an upgrade, as it's only 160MHz faster than what you've got. As long as the BIOS supports it (and very likely would if you're running the lastest version), i'm very confident a Core 2 Duo T5850 should work in that system, and is the fastest Socket P 667FSB processor you can get. If you're interested, i'd check eBay, as you can usually score chips like that for $15 or so.
This is NOT something the average person should be doing. Most laptops require quite a bit of disassembly to change a processor. The T3400 would not be much of an upgrade in your situation, and probably not even worth the hassle. The T5850 would be a descent upgrade. The problem you face is that your motherboard has a maximum of a 667 FSB, which limits how far you can upgrade.