you can put up a journal (next to profile/settings) where you can tell people whatever you want to tell them - about how's your day been or stuff
you can fav works of others if you like them (the button displayed under the picture) and you can devwatch people (in the general section on their page, in the middle) so you get informed when they upload new pictures/journals
to make sure people know that you answered one of their comments you have to press "reply" or in the message center go on "commentXXXX"
you can send private notes (middle of the page, next to "devwatch")
to give links you copy the URL address, or to link to an artists site you type :dev"nameoftheartist": or :icon"nameoftheartist": to show his avatar (the thing on the right upper side of the comment - to get one for yourself got to "settings")
hm... can't think of anything else important now.... as I said, feel free to ask me if you can't find it on (or don't want to use) the "help"