for the given application, truecrypt works well in linux too, as far as i have tested it.
but as mentioned before, for passwords only there are other options as well. since you may wanna save other data too and seem to know truecrypt already, i would give it a try.
an important thing to note: some text editors safe backup files of opened files... these may get saved to unencrypted parts of a harddrive. so it may be a good idea to add a text editor to the drive as well.