Apple TV with a household of more than one Apple IDs
This is possible.  You can log out of your Apple TV and have someone else log in.  This can get kind of annoying though. But it is possible.

If you have multiple computers in the house though, each with stuff bought with different Apple IDs, and you just want to access the content on the machines, that is very possible too.  You can set up home sharing with one Apple ID on your Apple TV and then on the rest of the other machines.  It has to be the same ID across the different machines but it will let you access all the computers that are on the network from the Apple TV and access and stream the content stored on them.

You can find a great tutorial over here.

You can still do things the old fashion way and log out and log back in, it can just be kind of tedious.  Home Sharing can really simplify the process if you just want to share content from multiple computers though.