BALTHAMOS  If you don't have Xcode, or are unfamiliar with programming, I have converted the application to Universal for you. All credit goes to the original developers of the program:

http://balthamos.110mb.com/files/Noise%20UB.zip  (Version 1.1)

XORCYST  For everyone asking for a universal binary, the source code is included and can easily be compiled as a UB with Xcode. I just did it, it works fine, and took all of ~90 seconds. Just convert the included project to newer xcode (it will tell you to do so on double clicking the file), set up the new project to compile for x86 and ppc, and build the new UB.  (Version 1.1)

ETHERL  When I first downloaded this, I used it for the same reason that most people use it for --- to drown out distracting noises. But then I had a baby. A very colicy baby. This program stops her crying & keeps her sound asleep better than anything I've ever seen! As soon as I turn it on & crank it up, my daughter stops crying. And it keeps her from waking up at night (I turn it down once she's asleep). It works faster than the kitchen fan/vent and it uses less electricity than the vacuum!  (Version 1.1)

JGILLMAN  I used this on my PowerBook G4 all the time, but I've got a MacBook now and can't use it! Would a Universal Binary be very hard?  (Version 1.1)