There are a couple good crabgrass killers out there. "Dimension" is in pellet form and is both a pre-emergent AND post-emergent if the stuff is caught early. I used this this year for the first time and am pleased with the results. I still have some crabgrass but not as much as usual and we had the ideal summer for it so, yes, it works.

"Tenacity" is another product that looks to be very good. I plan to try that next year (if the borders ever open so I can shoot down and get some!)

There are a couple others out there but these two seem to have the most promise.