Essential iPhone Apps for Internet Marketers Resource Center 

This simple but elegant app, designed by consulting firm Elite SEM, puts five classic marketing calculators at your fingertips: Cost Per Thousand (CPM), CPM to Cost Per Acquisition (CPA) Conversion, Banner/Email Campaign CPA, Cost Per Click (CPC) to CPM, and Maximum CPC for Pay-Per-Click. Just fill in the data fields and submit.

Other buttons give you the formulas to calculate these and other important rates such as click-through rate and percentage of campaign completion.

This app, created by ad research company Ad-ology, is both an at-a-glance source of industry news, trends, discussions, relevant Twitter posts and research in advertising and marketing and a good example of an iPhone application used for subscriber acquisition.

To see what we mean, open the app and tap on the "Current Buzz" feature. Scroll to the bottom and tap the field marked "Free Personalized Insights to Your Inbox." This brings up an easy-to-navigate form. Fill in your subscriber data (name, email address, company info., if any), and then choose your interest categories for targeted emails.

This app provides a wealth of information on how to make better presentations, but we're including it in our list because it also demonstrates cool ways to organize and present information on an iPhone that aren't possible on a Website or in a handout.

Two quick examples: If you want to save any of the hundreds of tips for better in-person speaking, Webinars or PowerPoint, just swipe the tip with your finger. That saves it to an internal checklist for fast review. Use the "accelerometer" (shake the phone) to bring up a random quick tip and then shake the phone again to generate a new one.

Search, social media and mobile come together in this app from marketing agency iCrossing. Plug in your keywords (link sends you to the company press release; find the iTunes link at the end), and it will search for results on Twitter and Digg and across thousands of blogs and other networks.

Say What? reports full results too: the complete Tweet or the full blog post should you want to investigate further. Finally, save your search history for recurring terms such as your company or brand names or regular keywords.

Complex analytics apps are great, but sometimes you just want to pit one keyword against the other and see which one gets more hits on Google. Enter the simple but highly rated WebFight! by a Dutch Web consulting firm (gratis version shows ads). Type in your two keywords, and WebFight! will search the Web, counting how many hits each term generates.

Email the results to yourself or to co-workers and then try another round because it's so addicting. When we pitted "email" against "e-mail," WebFight! declared "email" the winner.

The Wall Street Journal is one of the few news organizations that has figured out how to reorganize its online content for the mobile reader, especially taking advantage of the iPhone's many tricks for easy fingertip management.

Scroll through the daily headline list, and tap either to save a story for reading later or email it to a colleague (the app incorporates your email contact list). View video or listen to WSJ branded radio. You'll need a paid subscription to access all the online content, but what's available for no charge will give you a good enough picture.