It's all about rising above the noise.Some 150,000 apps line the App Store's virtual shelves, yet there's not yet a good way to shop for them. The App Store's oft-criticized search offers little assistance unless you know exactly what you're seeking. Marketers have been accused of gaming the App Store's customer reviews, both in positive and negative ratings.[ The iPhone should be a mobile commerce and social networking star this year, predicts CIO.com. | Check out the best of the best iPhone apps. ]What's left is the App Store's main Top 25 list, as well as the Top 25 list in every category. The bottom line is that many iPhone owners lean on these lists to tell them what to buy. "The Top 25 list is the thing that drives distribution," says Krishna Subramanian, founder of Mobclix, which operates a mobile ad exchange marketplace. "Other apps just don't get the exposure."For starters, getting on the Top 25 list isn't easy. An app needs to be promoted through mainstream media, marketing, word-of-mouth and social media to increase downloads and make the list. Big app developers know the score, too. Microsoft, for instance, poured marketing dollars to promote the Bing app on the iPhone in December in order to lift the app on the Top 25 list of its category.But app popularity is also a moving target, and it's easy to see how some good apps often fail to make the list and thus fall under the radar.Here are six cool apps that currently suffer this fate:The Extraordinaires: The Do-Gooder AppWhat's cool about this app: This app connects volunteer-minded individuals with non-profits, and lets volunteers do quick "missions" that actually do some good in the world. During the Haiti earthquake, for instance, you could fire up this app and help identify individuals within photos.Why it flies under the radar: CNN, Time and the Washington Post have covered this app, yet it's never really cracked the top hundred within its category. What's the problem? "Maybe the people who are interested in social good don't necessarily own an iPhone," Subramanian says. "It also could be that the coverage is focused on the website and not the iPhone app."Preschool Adventure: Education's Slow Learning CurveWhat's cool about this app: Software developer 3DAL makes a lot of fun educational iPhone apps for kids;Preschool Adventure is one of its more popular ones. The app lets parents and their preschool kids play six simple games, such as matching animals to dot-to-dot numbers.Why it flies under the radar: Education is one of the last markets to jump on a technology bandwagon, and this is true for the iPhone. Apps aimed at education, especially for very young children, are just now starting to come around.The reason for the educational delay is two-fold. For starters, early app developers targeted broader markets. Meanwhile, iPhone owners weren't used to handing over their iPhones to youngsters so that they could play with apps. But the iPhone is growing up.i.TV: Mobility in the HomeWhat's cool about this app: This app, an entertainment guide for upcoming cable TV shows, doubles as a TiVo remote. For folks annoyed with the slow Comcast TV guide interface, this app provides a faster way to find programs. You can also watch movie trailers, buy movie tickets, and even share what you're watching with friends on Facebook and Twitter. Now your iPhone has a place in your home next to your TV remote.Why it flies under the radar: This well-designed app gets overshadowed by apps tied to big brands, like Flixster, Fandango, TiVo, and Netflix. These apps have big marketing budgets and tap large numbers of existing customers. "It's difficult to compete with brands of that size," Subramanian says.HotelPal: Competing for RoomWhat's cool about this app: This app plugs into Travelocity and lets you search hotels and find rates and availability. Moreover, you can see pictures and maps and read information about the various hotels and then reserve rooms from the app. A very simple and clean interface makes this app super easy to use.Why it flies under the radar: This app made it onto Apple's iPhone TV ads and even got some coverage on the New York Times. But it hasn't had a huge amount of success on the App Store, in terms of downloads. That's because there's a huge amount of competition in this travel space from apps like Kayak and Hotels.com, which have been successful in pushing their brands.What to Expect: A Baby AppWhat's cool about this app: This app helps women track their pregnancies, with everything from a due date calendar to weekly baby illustrations and belly pictures. The app plays into a growing trend of healthcare apps that target specific people, like diabetics who want to track their insulin intakes and overweight people who want to track weight loss. "Apps are becoming more embedded in our daily lives," Subramanian says.Why it flies under the radar: Pregnant women are a niche market.SBSettings: Great App, One ProblemWhat's cool about this app: This app is a kind of toolbar that appears on the top of the homescreen or inside an app. You can quickly turn on or off Blootooth, WiFi, and 3G, adjust brightness, launch apps, and perform other functions without having to launch settings.Why it flies under the radar: The iPhone doesn't support apps running in the background. To run this app, you have to jailbreak your iPhone. This app doesn't just fly under the radar, it flies off the radar.What are your favorite apps flying under the radar? Send me an email at email@example.com. Or follow me on Twitter @kaneshige. Follow everything from CIO.com on Twitter @CIOonline.