I don't believe a discussion forum has any business choosing a site of the week, however they may perhaps be able to provide an avenue for the members to take their own polls, and have a "site of the week or month" posted as a result. Sort of like one of the contests mmg runs for ad space. The site could perhaps be rewarded in this case rather than a member.
It would help the winning site's traffic, along with mmg's since I'm sure folks would be lining up to vote for a site that they're involved with. Of course this would be for hyip/surf/mlm/cyclers etc..
Perhaps it's not really worth anyone's time, but it was just a thought.