I just noticed that the upcoming 2.6 kernels (since kernel 2.5.43) support two new filesystem mount options, dmask and fmask. dmask is "umask for directories", and it is the octal map of permissions that you do not want directories to have. fmask is "umask for files", and it is the octal map of permissions that you do not want files to have. Both default to the current umask of the user.
For example, if you have a VFAT filesystem being mounted which always sets the 111 bits for non-executable files, you can enter this line into /etc/fstab (this is just an example):
/dev/node /mnt/point auto defaults,fmask=111 0 0
This masks out all the execute bits on ordinary files that appear when the VFAT filesystem is ordinarily mounted, making your ls output cleaner if you use the --color switch. It also makes your system more secure IMO.
Only 2.5.xx (x >= 43) and 2.6 kernels support this feature; 2.4 and earlier kernels don't.
EDIT: Formatting problem.