Chikai Ohazama has made up a little Mac OS X-looking interface to all the Google services:

[...] which came about because I wanted a quick fun way to access all of Google's services. I gave it to a few friends in the company, who gave it to their friends, some posted it on their blogs, others sent it around on mailing lists, and it eventually made its way to Marissa Mayer, who liked it enough to say, when do you want to put it up on Labs? So after some spit and polish from some enthusiastic Googlers and the keen eye of the UI team, Google X is here. I hope all of you enjoy it - especially Mac users, who I'm sure will appreciate its lineage.

Click here to use it. I think it's a good thing, collecting their services; don't forget the Google Watch though!

edit: Google has removed the functionality. This may be because patents pending with Apple.

edit 2: now there's actually this replica of the original functionality, on a non-Google-loved page.