You can see who's online, by clicking the "Current Online Users" link at the bottom of the main index page..
http://www.iceinspace.com/forum/online.php
It shows what thread they're viewing, etc.
You can also set yourself as invisible in your profile, so that if you don't want to be seen, you can remain anonymous.. except to me.. cause admins can see all!!! mwuahhahahahaa!
You can also list your ICQ/MSN handle etc in your profile, so if people are interested they can look you up!