There is currently no mechanism built into Wikidot to automatically determine who is online or not.
One method you could use, but would require some work from your members is to set something up like we are working on over on the Live Support site.
Each support mentor has their own "member" page. When we are are online, we edit the tags on our page and add the "_online" tag to indicate we are online. When we go offline, we simply edit tags again and delete the tag.
We use the ListPages module on the home page to show who is currently online (by examining the tags on the mentor member pages). You can examine the page source on that site to see how it was done.
You will probably want to create a member _template page so your members can fill out a structured layout that will make it easy to display specific bits of member info, including images. Take a look at the mentor:_template page to see a good example.
You may or may not have more questions after digesting all of this. Let us know if you need more help.
BTW, there's no need to post the same question in multiple threads. It's unlikely your questions will be missed by the eagle-eyed community!
-Ed
