I just purchased a SquirrelMail skin setup from NutsMail. Pretty slick. I only have one them. It comes prepackaged with a bunch of plug-in directions, etc.
Just as an aside, it is a pretty nice setup. With the plug-ins that are available and with virtual hosting, I can use this platform as an interface to all of my e-mail accounts with alot more control and flexibility that I otherwise have (.e.g SPAM plugins, weather, fortune, virtual domains, etc.)