eric: I fixed it up for ya.
Okay, in the few hours that have passed since my first inquiry about changing the apple logo on the menubar, I discovered that there are NO tutorials on the internet whatsoever.
After trial and error, and the lone tip from "Benjamin" at Macrumors who posted a link to the app you will need to do this, I was able to figure out how to change the logo from the stock Aqua Apple logo to the classic rainbow Apple. You can use whatever you want to use as the new logo, but I have an affinity for that colorful apple myself.
DISCLAIMER: I AM NOT RESPONSIBLE FOR ANY DAMAGE TO YOUR SYSTEM. BY FOLLOWING THESE DIRECTIONS, I HOLD NO LIABILITY SHOULD SOMETHING GO WRONG WITH YOUR COMPUTER.
DO NOT MUCK AROUND IN THE SYSTEM FILES UNLESS YOU ARE 100% CONFIDENT IN YOUR ABILITY.
I would rather have a working computer with the blue Apple logo than a dead computer with no Apple logo.
Okay, enough technicalities.
First, you will need to download [URL="http://www.geekspiff.com/software/themepark/]ThemePark[/URL], and you will need to have a copy of Adobe PhotoShop (legal, of course!

)
Open up ThemePark, and go to File -> Open -> Macintosh HD/System/Library/Frameworks/Carbon.framework/Versions/A/Frameworks/HIToolbox.framework/Versions/A/Resources/Extras.rsrc and Extras2.rsrc
In the search box, type in "2030" and hit enter. You should only see "pxm#" in the far left column. Click that, then "2030 Root Menu Center", and then select the Blue Apple logo.
There is a button with a picture of the Photoshop CS2 logo (blue-green feather in a white box), which is titled "Send". Click that, and Photoshop will automatically open the Blue Apple logo.
From here, take the image of your choosing (in my case, the rainbow Apple), and open that. Resize both images until they're a similar size, in my case, expanding the blue apple about 200% and shrinking the rainbow apple 50% was enough to make it workable.
YOU WILL WANT THE NEW IMAGE TO BE SLIGHTLY LARGER THAN THE BLUE APPLE SO YOU CAN PLAY WITH THE SIZE WITHOUT TOO MUCH DISTORTION
Copy the new image over to the blue apple, and use Transform -> Scale to resize the image until it's the size of the blue apple.
Then shrink the image back down to 19x22 pixels.
Leave photoshop open and go back to ThemePark, and select the button next to the "send" button, which is "Recieve". Your new logo will be in place of the old blue apple.
Repeat the same steps on the white apple, if you so feel. In my case, I took my new rainbow logo, dropped the contrast and brightness, and made a black apple. (The white apple is what shows up when you click on the blue apple.)
Once you've done this to both the Extra.rsrc and the Extra2.rsrc file, click "Save As", and save them as "Extra" and "Extra2" to the desktop.
EXTRA.RSRC MUST BE SET FOR POWER PC, AND EXTRA2.RSRC MUST BE SET FOR INTEL. YOUR SYSTEM WILL CRASH IF YOU DON'T HAVE IT SET ACCORDINGLY.
Opening Photoshop CS after my first attempt at this caused my whole system to go down until I went back and made Extra.rsrc set for PowerPC. I made the mistake of making them both set for Intel.
EXTRA.RSRC IS POWER PC!
EXTRA2.RSRC IS INTEL!
Now, make a folder on your Desktop called "ORIGINAL THEMES".
Go back to /System/Library/Frameworks/Carbon.framework/Versions/A/Frameworks/HIToolbox.framework/Versions/A/Resources/, and copy the original Extra.rsrc and Extra2.rsrc to the ORIGINAL THEMES folder. Then, drag the original files from /System/Library/Frameworks/Carbon.framework/Versions/A/Frameworks/HIToolbox.framework/Versions/A/Resources/ to the Trash. You will be asked to authenticate the move.
DO NOT EMPTY THE TRASH YET
Copy your new Extras.rsrc and Extras2.rsrc from your Desktop to /System/Library/Frameworks/Carbon.framework/Versions/A/Frameworks/HIToolbox.framework/Versions/A/Resources/. You will be asked to authenticate again.
DO NOT EMPTY THE TRASH YET
Go to your ORIGINAL THEMES folder, and rename the original Extra.rsrc and Extra2.rsrc to ExtraORIG.rsrc and Extra2ORIG.rsrc. Move these from your ORIGINAL THEMES folder back to /System/Library/Frameworks/Carbon.framework/Versions/A/Frameworks/HIToolbox.framework/Versions/A/Resources/. You will be asked to authenticate again.
NOW SECURE EMPTY THE TRASH
Secure empty the trash and relaunch the finder.
CONGRATULATIONS! YOU NOW HAVE A CUSTOM APPLE LOGO WITHOUT PAYING $30 FOR SHAPESHIFTER!
If you have any questions, feel free to IM me or send me a PM.