Am I correct in thinking that the motherboard and ram slots have to support FBDIMM? That they cannot be used in regular pc's? Are there any uses for the ram besides finding an old server that supports it?
It appears that you cannot , a quick search of the net reveals an ancient article claiming that intel refuses to provide FBDIMM support in desktops.
This almost as old explanation says similar stuff.
So the answer is no.
You could re-purpose them as Iain says because its too big to be made into a key ring like I did for my old laptop ram.
You could could try building something like this http://www.instructables.com/image/FGME2MNGWF60K7J/Glow-in-the-dark-RAM-clock.jpg, other than that not really as it is only compatible with what it is compatible with, you cant change this. There are the odd few business / high end workstations that support this, but most use unbuffered memory.
I'm not sure if this is the same stuff but it appears to be compatible with a Mac Pro if it is, I also saw mentions of an Hp Business Workstation, but it may not be the same thing as you have http://www.bhphotovideo.com/c/product/616026-REG/Transcend_TS4GAP193G_4GB_2x2GB_Mac_Pro.html
The best thing is to Google the part number of the RAM and see what it pops up on Google as being compatible with.