When it comes to creating fun hacks for social networks, the easiest way to do so is by utilizing official APIs. All of the big guns have them, and I’m always interested to see what apps developers can come up with. Foursquare seems to be in that camp too, as the location-based network held a Hack Day at General Assembly in New York Saturday.

The company provided the workspace (along with the requisite pizza, energy drinks and beer) and had a seasoned team of engineers to help out the 150 developers taking part with any questions they had over the API. While not all of the developers were able to finish their projects in the allotted time, a bunch of neat apps were created as a result. Here are some of the most exciting apps created during the event:

Fourgraph

We all know by now that infographics are a great way of sharing a wealth of information in a practical, appealing way. I love them, and that’s why I like developer Jean-Luc David’s app, FourGraph. After linking your Foursquare account, it will display a map of all your check-ins and provide a wealth of stats.

What does my Fourgraph tell me? Well, that I’m an early adopter of Foursquare (user #200,039 of almost 7 million, thank you very much) but that I haven’t checked-in nearly as often as I should have — just 35 times, for four badges. Man, I have a lot of work to do if I’m ever going to catch up with our managing editor, Chris. Since my infographic is as about as barren as the Sahara, here’s Chris’ one instead.

Sadly, the map visualization doesn’t seem to work for either me or Chris, but hopefully that will be fixed soon.

Agora

Agora, created by Pierre Valade, hooks up your Foursquare profile to your Twitter account and promises to send you tweets when you check-in at a venue. The trick being that it will tell you who else is at the venue that you might be interested in meeting, based your Twitter graph.

It’s a nice idea, and I could see it being expanded to bring in date from the likes of Facebook and LinkedIn. There’s a lot of potential for this to take off at conferences and the like, so fingers crossed that Valade decides to expand the scope of this project.

4squareand7yearsago

For a heavy Foursquare user — which we have already established that I am not as yet – I can see this one being of interest. After linking your Foursquare account, 4squareand7yearsago will send you an e-mail each day detailing the venues where you had checked-in exactly one year before.

Here’s a look at an e-mail that was sent to Foursqaure founder and CEO Dennis Crowley after he signed up for the app:

I like the concept, as well as the fact there is a teaser of what to expect from your e-mails over the next week. It’ll be interesting to find out what happens on Feb. 29 in a leap year, though.

A list of apps created at the Hack Day is available to view at the event’s wiki page. Which is your favorite and why?

[Image Credit flickr, bentobox, dpstyles]