Man. I've stumbled around for hours trying to get a simple GridField happening in SS3. Finally came across [url=http://www.inforbiro.com/blog-eng/silverstripe-gridfield-tutorial/]this page[/url]; and guess what - it's working! Hope this saves some time for someone else.
Oh my god... thank you SO much! :-)
PS just for any newbies... a *simple* way to list all of the "contacts" on your site would be to add the following rough code to the "ContactListPage.ss" template:
<% control Contacts %>
<% if ProfilePicture %><img src="$ProfilePicture.URL" style="float:left;margin:20px;" /><% end_if %>
<a href="$Website">Visit Website</a><br/>
<% end_control %>