28xx switches do not support stacking.   You can connect the switches via a lag if you need more bandwidth.  connecting A-C would create a loop, but if these switches are in managed mode, they have spanning tree prtotcol which will prevent looping of traffic.   You may want to connect A to C for redundancy in case the links between any of the the switches go downm then spanning tree will bring up the extra connection.
I have three Dell Powerconnect 2848 switches in an environment with about 75 users. I just recently setup one in managed mode so that I could configure lag on the switch and make use of nic teaming on a new server. As of now the switches are connected with single patch cables from switch A->B and B->C. Should I be configuring lag on my combo ports so that I can have two cables from switch to switch? I have been reading about stacking where an A->C connection is made, but doesn't that create a loop? This is something I recently inherited and this situation strikes me as a bottle neck for workstations trying to access servers that are on different switches so any advice would be sweet.
best way to connect three Dell Powerconnect 2848 switches?