Xanthe, if you scroll right down to the bottom of the page, you will see "Your Tools" , and under that "Surname Interests". If you select that, you can see the interests of other members, and also enter your own.
You can also add your surnames and areas to your profile in your page settings. They will show permanently on the bottom of all your posts, as are mine on this post! I'm always looking at surnames on other peoples posts, in the hope that I might find someone else researching one of my families.
The search box Sarah mentions is a great tool too. 😄