IANONMAC  I've just watched episode 22 of Macbreak Weekly in which Merlin Mann recommends Menubar which as far as I know is the only way to completely remove the menubar.

Surprisingly there is still no version for Leopard and I would like to add my request for this.  
(Version 1.1)

EASER  For equivalent effects with Leopard, I use a combination of LeoColorbar (http://www.macupdate.com/info.php/id/26081/leocolorbar) and Menu Eclipse (http://www.macupdate.com/info.php/id/27686/menu-eclipse). Both are free and provide some nice customization.   
(Version 1.1)

BOXCAR  I like it! It is easier on the eyes and works well with 10.4.11  
(Version 1.1)

L0XBY  I wish they would make this Leopard compatible. Would be nice to dim the menubar when it's not needed.  
(Version 1.1)

CHRIS FAM  Oh my god, it looks like Leopard copied his idea! :-D  
(Version 1.1)

FREE_DEVELOPMENT  I just found out that not only does it shade, but can also become transparent... even invisible... great great app for those without 10.5  
(Version 1.1)

FREE_DEVELOPMENT  Works great. I have a laptop so I do not have to worry about the menu burning the screen but i do feel like I can pay more attention on windows that are open. The menu fading in and out is a nice touch as well. Although this is a simple application, I will always be using it now that I tried it.

One comment... if you could make the icon hidden it would be perfect. I just changed the Icon to something that looks cool. Other then that it is great  
(Version 1.1)

TUPRING  This doesn't work on Leopard, which I figured. Hopefully it will get updated. My Leopard Menu bar is Opaque!  
(Version 1.1)

TOMIS  Works great except the programs icon shows up in the dock, which is a show-stopper for me. Making the program a background-only app (by editing it's Info.plist) breaks the fake transparency feature.

Hopefully the author will fix this shortcoming by removing the dock icon and adding a quit button to the preferences window.

10.4.9 PowerPC  
(Version 1.1)

PHILL KENOYER  I also have this problem with Virtue Desktops. It only works on one desktop. Since this is freeware, it will probably never get fixed. Also, Virtue Desktops is now closing down shop, so only Leopard will save us.  
(Version 1.1)