Office store is available here. The Office store is a site from which you can download different apps for office 2013. You can consider apps like “Addins”. Ther are lots of fun apps to explore. From a BI perspective there some nice apps too. I have played around with Bubbles and Bing maps fro Excel 2013.
With the introduction of apps Excel 2013 has become even more versatile allready offering native support for PowerPivot and Powerview. I cant wait to see what developer come up with.