What is a unix command for deleting the first N characters of a line?

sed 's/^.\{5\}//' logfile 

and you replace 5 by the number you want...it should do the trick...

EDIT if for each line sed 's/^.\{5\}//g' logfile

Use cut. Eg. to strip the first 4 characters of each line (i.e. start on the 5th char):

tail -f logfile | grep org.springframework | cut -c 5-