How can I reduce heat transfer around my window unit air conditioners?
Two things come to mind:


Heat loss occurs much more rapidly when airflow is involved.  So do whatever you can to seal all those gaps.  Buy some compressible foam insulation (about 1" wide) and use it to make a tighter fit around the air conditioners.
Those accordion things don't seem to have much R-value.  Buy some rigid foam insulation and cut it to fit snugly behind the accordion.  You could even use some of those compressible foam strips to get an even tighter fit.