I allllways go the route of hiding in plain sight. It is SO much more effective than trying to be a wallflower.

Volunteer to do the dishes and things like that - everyone will love you for it, and it gets you slightly out of the way.

I'm also big on finding a heated conversation that others are having, and then standing/sitting with them and listening and just not really volunteering much else. So you're with people, engaged in a conversation, so others won't draw you out of it (for the most part) and chances are the people going at it will not notice that you're only rarely adding in anything.

Also... distraction via asking them questions is always useful.

"So, do you have a boyfriend yet?"
"No, I had a few interested, but I didn't like them very much.... so how's hockey been lately?" (Key is to answer, and then provide a topic change via asking them a question about their own... and a little bit of lying is ok when it comes to getting them off your back!)

"Why are you still single?"
"Oh, you know how it goes....I'm trying to not dwell on it. Say, how's your kid doing at school these days?"

And I find answering questiosn about work and school are pretty easy and simple things to just give them. They're family, they will ask. Doesn't mean you have to tell them a whole lot, but it's usually easier to tell them something more substantial than "it's good" so that they'll feel satisfied and stop asking more.