First thoughts were that Xslimmer (currently $6.95) would be a great application for my wife as a) she has just set up her own blog to support her personal training business and b) she has just bought her first Mac a 20″ iMac. 
Seriously, this application is right up my street. I just love all this “little” apps that help you tidy up and maintain your Mac. As they say:
“Xslimmer is a new, user friendly way to size down your Universal Binary apps, without losing any of their functionality. How is this possible?
It is achieved by removing the code inside the Universal Binaries that does not fit with your machine’s architecture, a code that never gets executed and just wastes your disk space.”
What I really like about this app is that it is so simple to set up and use:
I am not a big fan of reviews that quote verbatim from developers sites, especially when they are saying why you should buy their product, but in this case there are a few things that I know you will want to know:
How does it work?
Universal Binaries are often referred to by developers as “fat binaries”, and that’s for a reason. When a Universal Binary application is created, it contains several versions of the code: a version intended to run on PowerPC machines (like G4 or G5 Macs), another one meant for the more recent Intel machines. This ensures that the application will run on all the platforms that support Mac OS X, but the code that is not suitable for the computer you are using will never be executed, although it is taking up space in your hard drive. Xslimmer analyzes the applications you have installed and removes the unnecessary code, leaving only the most suitable version for the computer you are using, and thus reducing the space taken up on your disk.
Isn’t it dangerous to modify the binary data of applications?
Removing code that will never be run on your machine is safe. However, a very small number of applications may not function properly after they have been slimmed down, because they may check themselves to enforce anti-piracy measures. Xslimmer takes a number of precautions to avoid putting you in a position where an application cannot be used after being slimmed down. It provides a backup mechanism that can be enabled from Xslimmer’s Preferences, automatically storing a copy of the applications before they are slimmed down. It also provides the means to “blacklist” applications that you don’t want ever to slim down. The blacklist is automatically configured to ignore some popular applications known to perform integrity checks on themselves.
We recommend that you enable the backup option if you intend to reduce the size of an application that you will not be able to reinstall.
How much space will I save?
Xslimmer only reduces the size taken up by application code. Other application files, such as icons, images or support files are unaffected. The ratio of code to the total size of the application is very much dependent upon the nature of the application itself. Media-intensive applications, for example, show a lower rate of compression than those based on computing horsepower alone. BBEdit, for example, is reduced by 35%, whereas the reduction in Keynote is very low due to the huge amount of media files in the installation.
The size of Universal Binary code will probably grow in future months, as new architectures are introduced. 64-bit Intel microprocessors, for example, may require a third version of the code to be bundled inside Universal Binaries.
So …….. simple and effective on the outside, smart as anything on the inside. Perfect combination!