I have a Dell 24" as well (the old 2405), and it rocks. Dell uses Samsung panels I believe, so Samsung is awesome too. BenQ and Acer are also good I hear. I have had the pleasure to see some Acer monitors, and they are really good. Very reasonable prices too. When I was looking at 24" monitors originally, it was between the 2405 and the 24" Acer had out at the time. The only reason I went with the Dell was the extra input options and the height adjustment.
If I ever have to replace the one I have, I am definitely going to look at Acer and BenQ for sure.