We popped out to Kanchanaburi for a few days in early June '06. Kanchanaburi is a great out-of-Bangkok escape. The town itself isn't exactly charming, but the war cemeteries, museums, and of course the Death Railyway/Bridge Over the River Kwai are fascinating from a historical point of view. Plus, there is a well-developed tourist infrastructure too, making for lots of places to stay and to eat, particularly along the river area and just northeast of the war cemetery.
We spent three days and two nights in Kanchanaburi, which was enough time to explore the town, the bridge, and the museums, plus spend some very quality time doing nothing at our riverside guest house, just watching the water pass by.
We could have easily spent an extra night or two there as well, which would have given us time to do some of the out-of-town trips to the waterfalls and some of the many other outdoorsy things there are to do in the area.
As mentioned, there is a wide range of accomodation choice in town, but we decided to splurge a bit and stay at the River Guest House, so we could have one of the rooms that actually floats on the river. Sleeping at night was delightful, being gently rocked back and forth by the river currents, and the sunsets from our porch were stunning.
Travelfish does a great job listing the things to see and do in town, but I'd like to add one other museum that I think is particularly well done and worth visiting. It's the Thailand-Burma Railway Centre, located right next to the Kanchanaburi Allied War Cemetery. The museum is done in nine thoughtfully constructed galleries which show all aspects of the construction of the bridge and the lives of the prisoners and guards there. It's open from 9 am until 5 pm, and costs 60 baht per person. (Somtam, I have a pic and contact details too if you wish).
As for transportation, buses to Kanchanaburi depart from the Sai Tai Mai (Thonburi) Bus Station every 20 minutes or so, and cost about 100 baht one way. But we decided to take the train to Kanchanaburi instead, since it travels over about 60 km of the original route of the Death Railway. There are trains two times per day departing from the Bangkok Noi Railway Station in Thonburi (not far from and just across the river from the Khao San Rd area). It costs a flat rate of 100 baht for tourists, and takes about 2 1/2 hours to get to Kanchanaburi. The wooden seats in this all 3rd class train could reduce your bum to tears, but the views out the window and the historic journey are worth it.
To get back to BKK, we thought the best option was the tourist/backpacker minibuses that pick up at your guesthouse and drop off at Khao San Rd. They cost 130 baht per person, which, after you add up the costs of getting to/from the bus station in both Kanchanaburi and Thonburi, is actually a cheaper and certainly a more convenient option.
That's us for Kanchanaburi. Cheers.