Or find TinkerTool, it can toggle the visibility/invisibility of files in the OSX Finder.
http://www.bresink.com/osx/TinkerTool.htmlIf you unzip a Rockbox build or a theme and you can't find it, run TinkerTool, click on "Show hidden and system files" Most themes get unzipped in a folder called .Rockbox (note the period before Rockbox). Just rename the folder without the period and it will be visible.
What I have been doing to install themes or builds is to run the Terminal program (in Applications -> Utilities), type "cd " (note space after cd), drag the iPod onto the Terminal window and hit enter. Then type "unzip " (space after too), drag the theme or build onto the Terminal window and hit enter. If the files haven't been installed then you will see a list of files being installed onto the iPod. If there are duplicate files it will ask if you want to use the old files or replace them. Then quit the Terminal app to allow you to unmount the iPod.
Then I run TinkerTool to see if the files actually went where they were supposed to. Most of the time they do. Otherwise I move them by hand.
David