You can reverse the meaning of the square brackets by putting a ^ immediately after the [. In this case, the brackets will match any character that is not listed inside the brackets. Again, note that we use [^] with regular expressions, but [!] with globs:

$ grep dev.hda[^12] /etc/fstab
/dev/hda3       /               reiserfs        noatime,ro 1 1
#/dev/hda4      /mnt/extra      reiserfs        noatime,rw 1 1