If you click on the icon of the world, located in the navigation bar just above the message board, you can do a quick search on either today’s active topics or new topics since your last visit.

I'm new to this site- is there a way of marking threads as [already read], so you can tell quickly if there are any new posts?

No I don’t know of any way to mark posts as read. I watch the houses to the left of the forum titles and the little notebooks to the left of the topics inside the forums. They will gray out after you visit and will be in color if there is anything new since your last visit.
(Netscape and older browser versions may display light bulbs and folders.)

or

At the top and bottom of the forums, you will see the "breadcrumb" line. If you click the icon: of the world, you can access recent posts. Options include "New Since Your Last Visit," a listing of any new posts made since the last time you logged into the community, and "Today's Active Topics," a listing of all topics that have had posts in the past 24 hours.

Also under the "Tools" tab there is a "Help" link that gives other tips for using the message board, including different ways of being notified of new posts.

Hope this helps.

If you click on the member name (to the left of their post, in blue, just
above the members title or avatar) you can view the members public profile.
If the member wishes to make their email available, you can find it there.