I am aware of Thunderbolt Displays as being the only monitors that are currently able to Daisychain.
Although Mac Pro's are able to drive multiple monitors, each monitor needs it's own port on the graphics card, thus it's not daisychaining.
Mac Mini's with the discreet AMD card are able to daisychain 2 displays and an additional one through the HDMI.
Next year's integrated graphics, the 2012 Intel HD 4000, will be able to daisychain. Otherwise in 2011, MacBook Air's and base Mac Mini's along with the Quad Mini Servers can only support one monitor through the displayport.
I don't think you could ever just daisy chain Macs together without network adaptors, and even then only for file sharing. Years ago you could direct connect over serial to share files, and you can still do that with ethernet.