Cambodia
Unless you are flying in or out of Bangkok / Phnom Penh, due to Cambodia's primitive infrastructure getting to Siem Reap can be a nightmare.
If you are determined to travel overland, it's worth checking out the website below. The author is clearly an old Cambodia hand and his site is filled with regularly updated info, tricks and tips on how to get around.
www.talesofasia.com/cambodia-siemreap-guide-get.htm
And loads of other nice stuff on the rest of the site.
Search Been there