Superb price of £30 (free delivery until 27th September) for an iPhone wireless charger.
Next cheapest I found was about £50 on amazon or ebay.
The way it works... put your iPhone 3G/3GS in the special case, then when you want to charge it place it on the mat.
It takes the same time to charge as a normal wired charger
Most shops sell this for around £79.99