Before going off to the UK, I also managed to get in a couple of days in Chiang Mai, as well as the trip to Koh Chang. Chiang Mai is probably may favourite medium sized town pretty much anywhere in the world. The only place to seriously rival it, in my opinion, is Yogyakarta in Indonesia. Chiang Mai is pretty well documented with its abundance of Lanna culture, temples and surrounding hills, etc., so rather than bore you with more of that, I thought I'd just mention here a couple of places some of you might not know about.
First is the existence of Baan Tawai, a village about 30 km south of Chiang Mai which is devoted exclusively to handicrafts. This is where they make them, so you get not only an amazing plethora and range of products, but you also get them at ridiculously cheap prices. Most of the stuff is wooden, but there's also ceramics, metal work and some fantastic furniture. Basically to get there, go towards Hang Dong and take a left.
Another great place is the resevoir near Doi Saket. When the water's high it's an awesome view. It's pretty tricky to find, though, but it's on the other side of the motorway from the Doi Saket temple (itself well worth a visit). You turn off at the Chinese cemetry and follow the canal, wiggling through some idyllic little villages. Eventually you'll see the huge banks of the resevoir.