If you are carrying a lot of USB key drives and running out of space on them, here is a handy tip if you also own an iPhone. The iPhone has a disk too! You can use your iPhone to store documents on the go and view those documents too.
Here is a great review from Macworld of 3 apps that allow you to store documents on your iPhone. These apps are all less than $8 each – so you can’t go wrong trying all of them :-).
My favorite is Files, since its a WebDAV server and accessible from Windows/Mac and other iPhones…