How can I password protect specific folders?

[White Rook]

The closest thing I can find to do is just set everything to No Access then reverse that when I want to open it. Is it possible to bring up the administrator password popup to open a folder?

 

[Flying Meat]

You could use a series of password protected disk image files instead of folders...
Look at the options for the Disk Utility. You can choose to convert a folder to a disk image. Options for disk images is encryption and writable.
Probably not a good idea for individual default home folder items like ~/Library, Documents, Music...
It is possible to use File Vault to encrypt your home folder though, so you could just move those folders there before/after encrypting.

 

[Natobasso]

Are you protecting files on a network or on your computer protected from other users?

If you put your files in any of your user folders, another user by default, can't access them when they're logged in. A server is another story, as the previous poster points out.