Media survey firm Nielsen is reporting that as of the end of 2009, about one in five wireless subscribers in the U.S. owned a smartphone. That’s up significantly from the ~14% who owned them at the end of 2008, and adoption is only expected to accelerate in the coming months.

So what’s going on with phone apps, now that a larger chunk of the population is able to download and use them? Nielsen is seeing about 15% of mobile subscribers downloading at least one app in a 30-day period.

Perhaps not surprisingly, those who own iPhones are more apt to download apps compared to people who own Android phones, Palms or BlackBerrys. Far more apps have been developed for the iPhone, although Android is feverishly trying to catch up.

Which apps are most popular? It goes without saying that games – free and paid – are quite popular. But the four most popular apps are Facebook, Google Maps, the Weather Channel and Pandora.

And where are the news apps in all this? Not even on the radar screen, it turns out.

… Seems people are getting more than enough news blasted out to them 24/7/365 without needing to sign up for a special app to deliver more of it — thank you very much.