There are many Vietnam travel websites out there. Which website is reliable one?

Yes, there are many websites with attractive looking and information. You may get very useful information from them. But you got to be careful when you plan to make a reservation. You need to judge if they are real and reliable travel agencies or some sort of travel agencies running without International tour operator licenses (This is a must when some one wants to operate tours in Vietnam). Many websites are made by individuals (off course they have no licenses) or IT Company (Information Technology Company) who are good at information technology and information integration, but not real travel professionals. One trick is to WHOIS their domain name and sees the registrant is a travel company, or a tech company, or just an individual.