Actually,
the "new" away 3d 4, the one that uses the flash 11 gpu Stage3d stuff,
Does not support collada officially yet.
It looks like in the next release it will.
For now you could look at
https://github.com/away3d/away3d-core-fp11/pull/140 .
There are usuable DAEParsers (collada) by Tim Knip available there, sadly they don't seem to handle SRT animations right yet nor support shape animation (correctly, yet). I did not test skeletal / skinning yet. There is another parser but that is most rudimentary.
You will have to add the parser manually, and possibly jimmy it a tad to get the animations over (away3d relies on seperate tweener classes anyway as of yet, to do SRT animations). See away3d\loaders\parsers\Parsers.as and add the DAEParser.as file there.
Also you can see this pull request was closed very recently and development for full integration was set in motion.
Looks like we might expect a (more) finished parser soon.
MD5 is a Quake format as far as I know, If you want to use it I think the only way is to go through some other 3rdparty application.By no means ever ideal I'd say.
good luck, many cans of worms ahead ;)
Olivier