You could set up a conditional in this bracket format to display certain content to members of x groups, and other content to users that are not members of the groups:

[[?x[[S45:groupID1]]x[[S45:groupID2]]x[[S45:groupID3]]x::xTRUEx:: 
<P>You are a member of at least one of the groups...You are welcome to see the MEMBER content</P> 
:: 
<!-- You are not a member of one of the groups --> 
<P>You can see the default content</P> 
]]