I'm looking for a Linux Distribution that I can install on a USB drive that I can boot at any recent computer.

Here's what I want to be able to do:

Essentially, carry around my computer on a flash drive.

More practically, I want to be able to boot to my USB drive and have a Linux OS that will recognize NTFS partitions, be able to access a Network and perform rudimentary functions like email, Internet, Word Processing, etc.
Further, I want it to be a fluid system that I can change configurations, add or remove applications, save documents (to the USB drive in a docs folder) and update.

My purpose is two-fold. First, I want to experience the practicality of taking my own computer environment (complete with my current emails, documents, and other projects) with me everywhere I go without having to carry a laptop, etc. Second, I want to be able to use my 'computer' to access files on the 'host' pc and perform basic repair functions like virus and spyware scanning of the NTFS or FAT 'host' pc and maybe some other basic things.

Any suggestions? I've used Linux off and on for years, but I'm no technician - otherwise I'd have just built it myself.

Thanks!