Samba shares

Run as root:

mount -t smbfs -o fmask=444,dmask=555,iocharset=utf8,guest  //server/share /path/to/mount-point

This create a read-only share, for all users, including root.

Example:

mount -t smbfs -o fmask=444,dmask=555,iocharset=utf8,guest  //ariadne/videos /tmp/rapoldinet

Explanation:
fmask=444 gives owner, group and other read permissions
dmask=555 gives owner, group and other read and execute permissions for directories
guest mounts the share without any authentication.
iocharset=utf8 this is because Windows uses Unicode for their filesystem since Windows 2000. This way you are able to use special characters abroad ASCII in your filenames without running into problems.