Before I looked at this, I did not know that Linux could play on the PS3. Indeed it can. See
this wikipedia.
Be aware from the description, that you will wipe out the storage on the PS3 if you choose to do this.
The correct question on software, is what alternative programs are there to run that you need in Linux. With some effort, you can get some Windows programs to run on Linux, but this is not really what you want to accomplish.
OpenOffice has an excellent version made for Linux that is included in most distros of Linux.
iTunes does not run in Linux, but I use Banshee and Amarok to manage my ipod.
I don't use Sopcast, but apparently there is a bare bones version for Linux.
Fedora Linux uses Pidgin as an alternative MSN messenger application.
So I suggest that you use google to do your research on this to see if it seems feasible to accomplish what you want to do. Also use my link as a jumping point for your research.
What version of Linux you use is dependent on what you find seems the best to suite your needs, based on the wikipedia descriptions.
From my perspective, Fedora and Ubuntu are both good choices, but I am sure others will have ideas on this.
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"I love it when a plan comes together." - Hannibal Smith