you can't do this directly in Ubuntu. You could install
something like TrueCrypt to do the job for you, but that's a heavyweight
solution.

It might be simplest to just put the files you want to protect in a
password protected archive but beware, not all archive formats support
passwords. Personally, when I need to do this, I use 7zip, but you need
to install that from the repositories. I don't actually know which, if
any, of the 'out-of-the-box' archiving formats Ubuntu provides that
support passwords.

would a pass protected thumb drive work 4 u?

Not so, you will find 'Cryptkeeper' in the Ubuntu Software centre, I like the
way it works.

I had not noticed that before. I'll go and have a
look at it.

I'm using TrueCrypt at the moment, but it really is overkill for what I
need.

I store all of my password hints in Evernote running under Wine. It allows me
to synch my notes on my phone, laptop, and desktop. Evernote has the ability to
encrypt notebooks. That said, I don't bother encrypting my hints as my
passwords are all call sign variants, so my hints are just first names.

Yes! Create a new user. When you do this, there is a check box to
encrypt the users home folder. To avoid having to sign out give yourself
all privileges the administrator has.

Beware!! Forget your password, forget ever seeing your files again.