MCRes - I am stopping working on this, please pick this project up if you know how. Use Sizer or The Launcher Version as an alternative. Here is the source, if you are good at coding you will understand it.
You want to capture the Minecraft window (e.g. with Fraps) and upload the video to Youtube? - That's easy.
You want the video to have the right proportions and no black bars on the borders? - Hmm, you'd have to scale it...
You don't want it to look blurry because you had to scale it? - OK OK, tell me what this mod does!
This mod adds a button to the "Global Mod Settings" menu that can resize the Minecraft window to the YouTube HD video resolutions: 1280x720 (720p) and 1920x1080 (1080p).
No manual resizing by eye and mouse! Just click the button and start recording.
It also can save the configured window size and maximized/normal state and restore it when you start Minecraft again.
Note that it resizes the window so that the inner part (without the borders and title bar) will be sized correctly.
That means if you click the 1920x1080 button your actual window size (with borders etc.) will be bigger, e.g. 1930x1100.
So with a 1920x1080 display you WON'T be able to switch to this mode because the actual window size is bigger.
In this case use Minecraft's fullscreen option - press F11 - or get a bigger screen
The current video resolution is shown right above the new buttons if you want to resize manually and be pixel-perfect.
How to install Minecraft Resolutions:
1. Download the mod and locate your .minecraft folder. You can find your .minecraft folder by typing %appdata% in the search box in your Windows Vista or 7 start menu or on Windows XP go to All Programs>Accessories>RUN and type it in the run text box.
2. Install ModLoader and GuiAPI into your minecraft.jar, be sure to delete the META-INF folder.
3. Go to .minecraft\mods and past the .zip download of my mod.
4. Test it, if it doesn't work you should watch the video tutorial below.