When it comes to the type of applications iPhone owners use most, ones for checking the weather trump games, music, news and everything else.

According to an upcoming report on smartphone usage by online market research firm Compete, 39% of iPhone users cited weather-related apps as one of the three kinds of applications they use most frequently. (The Weather Channel app specifically was cited by 13%.)

A quarter of iPhone users said Facebook's was one of three apps they accessed most often, followed by game apps, at 20%. More than 10% pointed to music-related apps. After that, the more than 100 individual apps or types of apps cited by users fell to single-digit percentages, with most less than 2%.

In contrast to Facebook's popularity, only 2.4% of iPhone owners said MySpace's app was among the ones they used most often. Danielle Nohe, director of telecom and media-related research for Compete, said that gap reflects Facebook's demographically broader user base, which overlaps more with the phone's. "Whereas MySpace still focuses on a younger crowd."

She added that the firm surveyed iPhone owners about which apps they used most commonly to explore usage habits beyond downloads. A recent study by Pinch Media found that only about 20% of iPhone users return to a free app after downloading it. A month later, the percentage was only 5%. The drop-off for paid apps was even steeper.

The Compete survey showed that the kinds of apps downloaded most aren't* necessarily the ones used most often. Games and entertainment were the most popular categories of downloads cited by iPhone users, at 79% and 78%, respectively. Weather apps were third at 57%.

Data released by comScore last week showed that Tapulous' "Tap Tap Revenge" music game has been the most downloaded iPhone app to date, with one in three users jamming with it.

Games was also the top category for all smartphone users, with 37% having downloaded game apps, followed by music at 28% and entertainment at 26%. Weather was fourth at 24%.

For a third-party advertiser, running an ad on a less flashy but more frequently used weather app might be a smarter move than going with a new gaming app that someone uses only a handful of times before it is replaced by the latest hot game.

The Compete study also found that people are seeking out apps themselves rather than choosing based on recommendations from friends and family or simply by popularity. About 60% of both iPhone and all smartphone users said they found apps on their own. "I would've thought that people relied more on recommendations and what's popular, so it's surprising to see people actually spending time to self-discover," said Nohe.

If that's so, it bodes well for apps that aren't necessarily launched by prominent brands or heavily promoted. At the same time, a TV ad won't hurt. Nohe pointed out that the Shazam (music search) and Lose It (calorie-counting) apps got a boost by being featured in iPhone commercials. They ranked among apps used most often -- cited by 7% and 5% of users, respectively.

Pricing on apps for all smartphones appears to hit a barrier at $10, with more than three-quarters of purchases falling below that level. "That seems to be the price-point up to which it's a no-brainer," said Nohe. "After that, it becomes a purchase decision."

Among all smartphone owners, a much larger proportion of iPhone users had downloaded free apps -- 51% compared to 27%. Roughly the same gap was found comparing the iPhone to rival devices made by Research In Motion, Palm and Motorola. That disparity may change in the coming months with the launch of other device-specific app stores such as RIM's recently opened BlackBerry App World, making more free apps available for other phones.

Compete's initial Smartphone Intelligence report released in November found that 93% of iPhone owners had downloaded an app, compared to 66% of smartphone users generally.

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