I've watched Avatar and I still have the Glasses, so I'm curious can I watch 3D movies on youtube or something with these glasses?

I've tried some and it didn't work :S
Any ideas?

Real D 3D Glasses only work when there are two sources, such as the two projectors in a cinema, so unfortunately they won't work on YouTube if those are the glasses you have,

The glasses they gave you at the cinema work, as James Xuan said, with two different sources, most probably using polarizing filters.
Find a reflective material (water, a window, something metallic, etc), and try -while wearing the glasses- viewing the surface of the material with one eye at a time. If they are polarized, you will notice differences in the light reflected on the same point, seen through each piece of glass.
(I'm not 100% sure about this, but it should work (?))
http://en.wikipedia.org/wiki/Polarization_%28waves%29

Depending on the cinema different types are used, e.g. in slovakia in a cinema my brother visited shutter glasses were used, in the netherlands two way polorized glasses are most common. Either way, most are unusable at home, because all normal (plainer/youtube) 3D methods are color based, which decreases the quality of the colours, but works on all screens.

Actually there is one way to do it, provided you're in the mood to do some fun stuff and have some random materials (e.g. in school). Take a piece of half-mirrored glass and place it diagonally between two laptops of which one laptop is placed on the side. Rotate the screen of the second laptop so that it is horizontal (while the laptop is on it's side) and experiment a bit so that both screens have neatly overflow viewed through the glass (ideally set the screen resolution in such a way that they are equally big with a black bar below and above the screen on the laptop standing on it's side), next start the left and right eye movie on each laptop separately and look through the glass with your glasses and you will see one of the most interesting 3D experiences ever :) GOOD LUCK :P

There's a lot of 3D content on YouTube. Some of it doesn't work properly, but some of it is fabulous.

Start with this video:

Assassin's Creed
youtube.com/watch?v=822kH5Fu8SM

You need to view it at YouTube, not embedded on another site.

Under the video there is a drop-down box that lets you choose what kind of 3D viewing you want, depending on what kind of glasses you have.

If you don't have any glasses, you can get the 3D effect without any glasses. Just choose the "Parallel" option, and you will see two images (for left and right eye). Let your eyes go a little cross-eyed so that you see three images, and the middle one will be in perfect 3D.

It takes a bit of getting used to, but if are able to view 3D stereogram photos (the kind with all the squiggles) then you will have no trouble with this at all.

Once you have mastered the technique it's easy to slip your eyes and brain into 3D mode. Now that you know how it works (on a "known-good" video), you can start exploring all the other 3D content at YouTube. Start with "Related Videos", or do a search for 3D.

Also see this previous Blogoscoped article:
http://blogoscoped.com/archive/2009-07-20-n37.html

Thanks James!
I'll try out what Zim and David said, I'm interested to see the result =)

Roger
I've tried the YouTube effects while waring the glasses and it didn't work, probably for the reason James mentioned. However, I'll give the parallel one a try.

MZaza,

If your glasses are polarizing, you need two pieces of polarizing film. Attach one piece to each side of your monitor – but rotate one of the pieces by 90 degrees.

Now use the "Parallel" setting on YouTube. You'll still need to make your eyes merge the images (the same as if you're not using glasses), but now you should see just the 3D image without the distraction of the other two images.

If the effect doesn't look right, just change which piece of polarizing film is rotated by 90 degrees.

An A4-sized sheet of polarizing film costs about $10.