I have no idea what I'm doing...

Alright, so I'm over exaggerating, but I still am stuck. I have 4 newly squired servers from my college. They are: POWEREDGE 2900 - with 2 dual core Xeon 3.2GHz - 4GB of RAM - and a RAID0 config - x3 146GB 10,000 RPM 3GB/s HDD's adding up to about 446GB of space. POWEREDGE 2800 - with 2 dual core Xeon 2.8GHz - 8GB of RAM - and a RAID0 config - x5 36.4GB 15,000 RPM 3GB/s adding up to about 160GB of space. POWEREDGE 2600 - with 2 single core Xeon 2.4GHz - 3GB of RAM - single RAID0 config - x1 73.4GB 10,000 RPM 3GB/s. POWEREDGE 2600 - with 2 single core Xeon 2.4GHz - 1.5GB of RAM - single RAID0 config - x1 73.4GB 10,000 RPM 3GB/s. So basically, I would like to know what I can do with these. I am hoping I can do something with the 2600's like use them as a small render farm for Blender? Is that possible? And the 2900 with Ubuntu 16.04.1 LTS, I am already using as a dedicated media server hosting films and making accessible with Apache2 as a website. As for the last 2800, it also has Ubuntu 16.04.1 LTS running as a game server for MINECRAFT. Don't get me wrong, all this is working absolutely perfect. I just don't see these as using them to their full potential. I mean, com'on, I have 4 PowerEdge servers! Freaking beasts, even if they are a little old (okay a lot old). So in all, like I stated, I just would like to know if this can happen and what they can really do. Also, if what the max RAM and CPU components they can contain would be helpful. (Bring on the tech talk please.)