Well, here is an update on the not-so-wonderful Tuk-Tuks. Yes, at first they are nice but the originality wears off really quick. But what you must really watch out for is the 10 Baht tours and the really cheap rides. They will stop off at various clothing stores and make you stay there for up to 15 minutes and they will often make you go to "just one more". It gets very very old very very quick. And unless it is a very long trip across town don't pay more than 40 Baht or so without the stopovers, you must be very clear about "no stops". I recommend the bus or just walk.

A typically Thai method of transport in Bangkok (and beyond) is the three wheeled tuk tuk - particularly practical on short journeys (the shorter the better, given that you are exposed to plenty of pollution...noise and air). You need to have your wits about you when you take a tuk tuk - drivers tend to speak less English than taxi drivers, they can take you to places you don´t want to go (usually gem stores, where they get a commission) and there have been some isolated incidents of robbery on women passengers late at night.

While buses are the primary source of public transport in Bangkok, the boats (or water taxis) are an interesting alternative (as cheap as buses, and you avoid the traffic jams). Boat services are very regular although the range of destination is limited by the water ways themselves. You can save a lot of time by the boats - for example, a trip from Banglamphu to the GPO will take about half an hour by water, half what it would take on land.