Here is what people did on mobile devices in Q3, by number of impressions (report)

We have entered the golden era of mobile advertising.

The sector is expected to grow by over 300% in the next five years and represents a crucial part of monetization for giants like Google and Facebook, as well as small startups.

Millennial Media released its “Mobile Mix” report today, looking at key advertising trends with a focus on mobile manufacturers, devices, operating systems, and connected devices.

Apple topped the lists for both manufacturers and devices, as ranked by impressions. Three of the top four devices were Apple, and it took 35% of all impressions, a majority coming from the iPhone.

When iOS 7 was released, impressions grew at an average of 185% a day.  Impressions from communications apps were nearly three times the average volume, and impressions from lifestyle and sports apps in iOS7 were six times the average volume.

Samsung ranked second for manufacturer and device, attracting 29.58% of total impressions this quarter.

Blackberry, LG, and HTC followed at third, fourth, and fifth.

73 percent of total mobile impressions this quarter were from smartphones. Android was the largest operating system by impressions this quarter. Fourteen of the top twenty devices were Android.

Millennial Media also looked at mobile developer trends.

Games was the number one category for impressions this quarter, followed by media and entrainment, mobile social media, communications, and productivity tools. Sports apps entered the top ten list this quarter, and 60 percent are soccer-specific apps. People love their soccer.

The report cited another study by comScore that examined which categories are more popular with people on mobile devices than desktops.

Consumers spend more time with photos, maps, games, weather, and social networking content on mobile. Retail fluctuates around the 50/50 mark, but Millennial Media said the emerging trend is towards consumers getting more comfortable with shopping on mobile.

When ranked by click-through-rate (CTR), smartphones are the clear leader for productivity and tools, sports, and shopping and retail. Tablets are the main choice for books and reference, and travel and local content.

Mobile is clearly the future, although VentureBeat’s John Koetsier (and resident mobile ad expert) said there is one main caveat — there is a significant difference between revenue per click on mobile and revenue per click on desktop. Desktop ads still bring in proportionally more revenue.

Juniper Research predicts that the fastest growth area in mobile ads will be in-app advertising, along with mobile Internet and messaging.

Millennial Media was one of the top 10 mobile advertising companies featured in VentureBeat’s mobile advertising index. It is the leading independent player for mobile ads outside of Google.