which is the best linux to install on a pendrive?

Almost all Linux distributions can be installed now a days on a pen drive. But if you want something light and something which has a small foot print as it should be in case of the pen drive then i would say use a distribution called Puppy Linux. Please have a look at the following website:: www.puppylinux.org/ take care.

I will tell you this: As long as you can boot from a pendrive you can install whichever Linux you want on it. How big is it? If size is not of importance go with Ubuntu. Works great for me :) Although I don't know how it will do installed going from different computers with different hardware. But that's my recommendation. Otherwise to just extract a LiveCD to a pendrive, such as knoppix. Most distros come on LiveCD now so you can try them out - distrowatch.com has a list of distros as well as they are sorted by popularity :)

knoppix linux is a great linux distribution..You could download aimage for free. once you have downloaded just copy the boot code and iso image to your thumbdrive.. once done with the command prompt boot from the .iso image without have to install linux to your thumdrive.