"You don't need to add a period to the beginning of a name, you can use the invisibility bit which is part of the Apple HFS+ file system via the leopard command in a terminal:
chflags hidden ~/MyFiles
This hides your MyFiles folder. You can read up on that command in detail here:
chflags MAN page
Daring Fireball: invisibility bit
You can also toggle showing hidden and unhidden files in finder using this applescript (I compile it to an application triggered via quicksilver):
set onOff to do shell script ""defaults read com.apple.finder AppleShowAllFiles"" if onOff = ""NO"" or onOff = ""OFF"" then set newState to ""show"" set OnOffCommand to ""defaults write com.apple.finder AppleShowAllFiles ON"" else set newState to ""hide"" set OnOffCommand to ""defaults write com.apple.finder AppleShowAllFiles OFF"" end if
display dialog ""Are you sure you want to "" & newState & "" hidden files? (This will restart the Finder)"" buttons {""Cancel"", ""OK""} default button 2 copy result as list to {buttonPressed} if buttonPressed is ""OK"" then try tell application ""Finder"" to quit do shell script OnOffCommand delay 1 tell application ""Finder"" to launch end try end if
Password protecting folders? The way I'd do it is make an encrypted DMG using disk utility and mount it when needed. You could get fancy probably and change the DMG icon to a folder icon, and hide it using the invisibility bit for full on effect :-)
If you want to spend some money doing it: Espionage"