netmeg - 2:21 pm on May 13, 2011 (gmt 0)
Whatever makes the most sense for you and for your potential users. Are the five topics related enough so that it makes sense for them to exist on the same site? Will people interested in one topic be likely to be interested in some of the others? If so, then just put it on the one site. If not, then separate them out.
(If it were I, and I was worrying about how Google would handle it, I would also look at what's already out there as far as competing sites; the sites with the least healthy competition would probably the the first ones I'd break out on their own)