If you click on someone's username (try clicking on mine - "David") you will get a drop down menu with a number of options. Most of these used to be buttons found at the bottom of each post in a thread but are now compacted here.

They are:

1) View Public Profile
2) Send a private message to David (If the member is accepting them)
3) Visit David's homepage! (If the member has one)
4) Find all posts by David (This is the search option for posts made by member)
5) Add David to Your Buddy List

Hey, that's a particularly cool feature :)