Many little rafts is probably a better idea than one big one.  That way, a mistake by one won't drag them all down.
The metaphor breaks down but there is nothing hindering nested peak oil rafts.

From fairly well managed countries and states to regions with significant hydro power and nuclear power to towns with good peak oil infrastructure to cooperating small size companies to cooperating neighbours to fairly self sufficient families.

Preferably organized in different ways to give better redundancy and competition that inspiers others via the net and the market. Then it will not hurt as much if some of them fails and others can learn from their failures.

There is no optimal solution. Therie is no golden road. The best I can think of is to on manny levels have social processes for finding better solutions all kinds of problems.

I'll put in a plug for my favorite liferaft builder: Post Carbon Institute.  From my point of view, rebuilding from the bottom up makes a lot of sense, given that the top level (Federal Goverment) is ineffective and out of control.  Rebuilding at the grassroots also empowers individuals to actually do something about the problems.
My contribution to a raft idea would be electric trolley buses.  Not as good as electric rail for urban transportation, but quick, cheap and easy to install.

Try to run one within 800 m, a half mile of everyone in an urban area.

Minimalistic, but useful.

Not only useful but a thoroughly demonstrated technology. Also, it occurs to me that the extra labor required to build the overhead rails might help to mitigate the huge unemployment problem that PO will sooner or later trigger. We can never do only one thing.

Also, the electric trolly buses I've ridden on in San Francisco seem nice and quiet and of course free of fumes . . . and reliable.

Would you like to run for president on the Electric Party ticket?

"Let's electrify transportation."

"Electrify now!"

"If elected, we shall electrify you within four years."

In Vancouver, BC they've been running Electrolic trolley buses for 50 years.  They run throughout the city.

While they are getting old, and are due for an upgrade before the Olympics in 2010, they definitely serve their purpose well, and who knows how much smog and money (due to very low electricity rates in BC) they've saved the tax payer over that period.

My greatgrandfather was a Victoria BC streetcar conductor!