Regarding the Singapore tours offered by the airport - I received the following information yesterday from Singapore Airport in response to my e-mail asking about the tours, transit hotels, and luggage lockers:

We are pleased to learn of your interest in joining the Free Singapore Tour at
Changi Airport. The Free Singapore Tour is offered to transit/transfer
passengers with at least 5 hours of connection time to spare. The 2 1/2 hours
tour covers the city and includes a bumboat ride on the Singapore River. There
are 8 tours a day at 10am, 1pm and at every hour after 1pm up to 7pm. Due to
its popularity, the Free Singapore tour is offered on a first-come-first serve
basis and no pre-booking is allowed. Passengers who wish to join the tour have
to register personally at any of the tour counters in Terminals 1 and 2. You
will require your passport, completed Immigration embarkation/disembarkation
card and air ticket for onward flight during registration. The tour counters,
which are located at both ends of each terminal, are opened from 8.30am to
6.20pm daily. You can approach our Customer Service Officers for directions to
any of the tour counters.

We are pleased to inform you that you can use the swimming pool located at the
departure/transit lounge east in Terminal 1. The Transit Hotel operators M/s
Harilela Holdings (S) Pte Ltd charges S$5.15 for the shower facilities which
includes towel, soap, shower gel and shampoo per use.

We are however sorry to inform you that all the electronic lockers in the
transit area of Changi Airport were not operational due to security reasons.
However, the operator, Manila Construction is operating a manual Left Luggage
Service in the locker rooms in the transit lounge of Terminals 1 & 2 from 0700
to 2230 daily until the electronic locker resume operations. Passengers are
advised to use the hotline phone on the side of the lockers to get details on
the locations of the Left Luggage Service.