I've found a great bag that fits the S90 with great protection, easy accessibility with velcro enclosure and best of all, a very functional belt loop enclosure but even better an easy clip on karabiner which you can snap on just about anywhere. The bag is snug but the camera comes out easily. The only drawback is there is no accessory pocket for an extra battery but for around town shooting where you don't need extra juice, this is a good one. If you want something a little larger in that line, the Kata DP-413 seems to fit the bill with room for both battery and card. I just ordered it also.

http://www.kata-bags.com/Product.asp?Version=Photo&p_Id=477