The link to the very last regular installment of Irregular Webcomic, at least as far as the actual strip, is here.
After No. 3182, the 2011-10-13 strip, which pretty much ends or ties up the various narratives to the extent that David Morgan-Mar is willing to do so, comes a slew of guest strips and a final annotation describing the end of the whole thing and to an extent the beginning.
After that the new material comes in two forms, one which was originally intended: just weekly essays where the annotations used to be, and a title graphic where the strip used to be.
A saving grace is that DMM is re-running the original strips now (not part of his original plan) with new annotations.