I want to list all of the applications and versions installed on my mac. Stuff like perl, php, etc., not the stuff you see in the Applications directory... Is there a unix command for that?
Not exactly a unix command but:
system_profiler -detailLevel full > myreport.txt
might be a good start.
There's an option to only list software (as there is an option to ouput xml) (read the manpage for the precise syntax).
If you're using macports you could just run port installed
.