Excellent posting here about Exchange transaction log files, in particular what to do if your transaction logs disk fills up.
Kind of handy when you come back to work after a week and the log file disk is full. ;-)
The main point I got from it was the fact that you do not necessarily need all of the transaction logs for a storage group. So say if your disk has filled up with transaction logs you can run eseutil to find out which log files you actually need and move the rest to a temporary location. This should then buy you some time to run a backup to flush the rest out properly.