This example installation uses rear-projection from three projectors, powered by three Macs running Quartz Composer 3. Local network using NetGear Gigabit Ethernet switch. The system is one I've created myself, called "ygboX", which synchronises multiple video clips across multiple displays to create seamless presentations.
This was created for a client's stand at MarkEx convention in Sandton.
Graphics were mostly done in Apple Motion, and edited in Final Cut Pro. The original canvas was composed in 1950x500, which was later split into three 640x480 clips.
The Macs are all quite old - two G4's and a single-processor G5 - but all running OS X Leopard 10.5.3 and Quartz Composer 3 (which has networking capabilities).
Download the software, or get involved with development, by visiting http://sourceforge.net/projects/ygbox