Nice! Oh yeah -- Happy B'day:)
I can see that they're AMD powered and have seen some really nice ones elsewhere. These tend to use quite a bit less power than the Intel powered systems. How much memory do they have?
I've seen things like these called main controllers too (relatively common) along with system controller, central controller and similiar. But maybe you're looking for a more greenhouse/AP centric name. I wish I had one. I call my house monitoring machine clever names like 'house1' or 'house2'. How about 'greenview' or 'fishweb' system? Or something more general like 'enviroserver'. I kinda like that last one since it doesn't exclude control and is applicable over a wide range of uses.
Looking forward to seeing what you use for a linux distro. DamnSmallLinux has a lot of appeal to me but I couldn't find a valid image of it to try though I did find a list of debian packages that they used.