Here's how things look at the Linux/Mac meet and greet:
Mac, may I introduce Linux.
Apple Filing Protocol, meet Netatalk.
Bonjour, this is Avahi.
They are, in short, Apple services and their open source counterparts.
My process of setting up an HTPC did not involve purchasing a mini mac, rather I repurposed my trusty and well-worn Cube PC as a newly reformatted 500GB Ubuntu 11.04 file server.
For seamless file serving, the UCube now utilizes Avahi and Netatalk to provide intersection to my LAN. When you gather crumbs of info to make your own similar setup, I recommend you use a succinct, updated guide such as Sidi Kahawa's. Though hundreds of responses exist on the older stalwart of this process, most of them have been fully addressed. It's close to turnkey at this point.