So now that Twitter is on the verge of becoming “So last year!”, what’s the new shiny, social media bauble for 2010?

Is it Foursquare, which is pushing the “Here’s where I’m located” phenomena with a service/game that encourages people to become the “mayor” of anywhere and anything? Given the chatter I’ve seenon Twitter about someone becoming the “Mayor of The Gap”, Foursquare looks to have some potential.

What about Posterous, which captured a lot of buzz a few months ago as a cross between Twitter and blog, particularly when well-known blogger Steve Rubel unveiled plans to use Posterous instead of blogging. While Posterous continues to launch new features, the buzz seems to have died, making it a unlikely 2010 social media “what’s next” candidate.

Another candidate currently on the fringes is Hot Potato, which offer a service for real-time social collaboration among people who can share an interest in an event as it’s happening. Leveraging wireless technology, Hot Potato users can filter by location, social graph or “presence” at an event.

Then there’s Blippy, a new (and strange) social media service (in beta) that lets people share their credit card purchases. For example, instead of doing a tweet about your Boxing Day activity, Blippy would automatically announce that you had just spent $49.85 at Banana Republic.

What about Google Wave? There’s been lots of buzz given it’s another Google service but so far Google Wave has been underwhelming, mostly because few services have been created to give Google Wave some sizzle.

So, what are your candidates as the best-thing-since-slice-bread social media services for 2010?