Down at number 26, is my Tombstoner helper library, which was apparently being used in 307 (or about 1% of all) apps.
It is of course very flattering to know that it is being used so widely and helping developers improve their apps. What I find interesting is how it compares with some of the other libraries available. There are a number of other libraries which have much higher download numbers (both in Codeplex & NuGet) and yet are much lower in the list. This shows that you can't take download numbers to strongly. It's actual usage that counts.
The sad thing is that with the forthcoming encryption of XAPs such analysis of the marketplace in the future will not be possible. :(
BTW. I am still planning on another version of the library. Stay tuned.
If you've built Windows Phone or Windows Store apps you can cross-promote them with AdDuplex to get more users.