I'm certainly no expert either but the way I understand it, it's one of the main branch of mathematics, where by that I mean that it pops up everywhere. ODE, PDE, geometry, you name it. Maybe not group theory itself but a closely related ramification such as modules or whatnot.
For instance, I'm reading the PhD thesis of a student at my uni at the moment and he introduces a homological method to prove new existence and multiplicity theorems in critical point theory.
As always, maybe if you asked specific questions, you'd be more likely too get an answer. I think matt grime is an algebraist but I haven't seen him in a while.