Animation standards and retargeting

I’ve been thinking of buying some animation assets to use for all my future games. Up until about a year ago I didn’t even know you could re-target animations from one rig to another, but I also heard it doesn’t always work. What is the current standard rig for animating that can accept re targeting from many different bone setups. Currently I am using 3ds biped. Is there also a easy free tool that will re-target for you from one rig to another? Also what is the standard animation clip file type? Info on animation standards in 2014 would be appreciated.

Finally. Could anyone recommend some animation packs for games that can cover a lot of animations, that over time I can have a solid library. I like shooter games a lot. I’m thinking a death animation library, shooting library, melee library, and motion library would keep me good for a long time.

Also any info on re-targeting would be appreciated I do not fully understand it. Thanks

Also what animation software is the standard now?