Yelp, which is consistently ranked as one of the top 100 free apps in the U.S., said its mobile apps were accessed on 5 million unique devices every month through the most recent quarter, according to its IPO filing today.

That minority of users, who make up about 8 percent of Yelp’s 61.1 million unique visitors per month, are potentially the most valuable. They account for 40 percent of all searches on Yelp’s platform for the quarter, according to the filing.

“Almost every second on average, consumers used our mobile app to look up directions to or call a local business for the quarter ended September 30, 2011,” the company said in the filing.

Yelp’s numbers give us insight into the volume of traffic and engagement that the biggest apps that aren’t games are seeing. The best-known games, of course, still attract large multiples over the usage Yelp sees. Zynga revealed in its most recent amendment to its IPO filing that it has 9.9 million daily active users on iOS and Android. (That is a daily figure, as opposed to Yelp’s monthly count.) Rovio Mobile also said recently that it has 30 million daily actives for its game Angry Birds. Their figure would also include usage on other platforms like Google Chrome.

Overall, Yelp reported a net loss of $3.8 million on total revenue of $22.3 million for the most recent quarter. It plans to raise up to $100 million in its public offering.