Grab list of Stats, Application Data, and Serials off OSX 10.6 to prepare for reformat and fresh install?
Most of what you need (i.e. hardware, network information, software etc. thats similar to what Belarc Advisor returns) can be obtained using the built-in System Profiler application (/Applications/Utilities/System Profiler.app). 

You can then export the information to a file using File ➔ Save As.., then select either "Plain Text" or "Rich Text Format" from the "File Format" dropdown.

The above can get quite verbose, so if you just want a quick snapshot of installed apps (including those installed by default, of course), you could start the Terminal (/Applications/Utilities/Terminal.app) then type

ls /Applications 

or 

ls /Applications &gt; ~/Documents/apps.txt to send the output to the file apps.txt in your Documents folder.