Here is my suggested order for getting into Vietnamese using online courses. For reference, I would put myself as recently entering A1, so this list may change as I progress.
Note that there are two major dialects of Vietnamese, northern (e.g. Hanoi area) and southern (e.g. Saigon area). I will try to provide resources for each when possible.
Step 1: Learn the Sounds
The first step to learning any language is getting familiar with the sounds. Listening to spoken materials is great, though it is likely to be overwhelming as a first step.
Step 2: Learn the Pronouns
Like many Asian cultures, Vietnam has a complex system for referring to others based on age and social standing. Learning this system is key. My recommendation, given the number and complexity of terms, is to draw a chart with people you are likely to communicate with, and focus on learning the pronouns that apply to them.
Step 3: Dive In!
One of the better comprehensive courses is over at Duolingo. Note that it was released just a few weeks ago and is still undergoing revisions. Pair it with the matching vocabulary course over here.
Step 4: Drive On
At this point, you can start to get a feel for the language by reviewing sentences and application of some of the basic words learned earlier.
Step 5: Advanced Material
Once you have become familiar with the sounds and have developed a sizable vocabulary base, it is time to start looking for native language material. Again, developing a matching vocabulary list here may help facilitate learning.
VTV – Sunrise (Free) - northern dialect only
Vietnam Television (VTV) is the national broadcaster for Vietnam, and the linked channel is some of the programming for children. Many short videos that area easy to listen to as you advance in your learning. Off youtube some of the same programming may be found at quà tặng cuộc sống. Another set of children’s videos may be found at Zing Kids.
Easy Languages – Vietnamese Playlist (Free) - southern dialect only
Easy languages is a great resource for street interviews on various subjects. The Vietnamese videos are limited to Hồ Chí Minh City, though a lack of comparable videos elsewhere makes it useful. There are only 4 videos.
Zing MP3 (Free) - northern and southern dialect
All the music you could ever want in Vietnamese. A fair number also have lyrics that follow the music (note that this does not show on the mobile version of the site). There is an app for mobile devices, though it does not appear to work in the U.S.
FPT Play - northern and southern dialect
Videos in Vietnamese. A mix of television shows, video, and children’s programming. The available channels cover many things - sports, drama, news, video games, and more.
A collection of movies and songs that I think are useful for active listening practice:
Xin lỗi … anh chỉ là thằng bán bánh giò! (Southern) - short and emotional movie.
Dấu Mưa - Trung Quân - slow song.
Xe Đạp - Thùy Chi & M4U - slow song.