Mobile apps have become an embarrassment of riches for iPhone and Android. In a world with over 500,000 iPhone apps and over 250,000 Android apps, the toughest part is finding the most useful stuff.
For iPhone users, I'm going to throw you an assist by sharing my top 20 (this is an update of my 2010 iPhone list, and I will update my top Android picks next week). My iPhone picks are all third-party apps that can help you be more productive, streamline regular activities, reduce the number of gadgets in your life, and take advantage of the top benefits that mobile computing has to offer.
Dropbox is a great cloud service that automatically syncs a folder of files between multiple computers (Windows, Mac, or Linux). This app extends Dropbox to the iPhone and includes a built-in reader within the app for PDFs, image files, and Microsoft Office files.
Once you get used to typing on a virtual keyboard (and it honestly took me over a year to do it), then these devices are great for note taking, and Evernote is a great note taking app. It is similar to Dropbox in that it saves data locally but syncs it across all your machines and devices.
There are a ton of to-do apps on iPhone but I prefer Due for its simplicity and its audio alerts. However, this is an iPhone-only task list. If you want something that can sync with your PC, Mac, or the Web, then try 2Do or Things.
I love Tripit. It is by far the best app I've found for keeping track of all my travel itineraries. It is powered by some excellent backend systems. You simply forward your confirmation emails (or use the Gmail plugin to do it automatically) for your flights, hotels, rental cars, and more to Tripit and it automatically organizes them into trips with all your details and confirmation numbers.
For some reason Google doesn't have an official app (for either iPhone or Android) for Google Analytics. The best one I've found to go deep into all of the data is Analytics App.
Even better than Analytics App for a quick-glance dashboard is Ego. It shows basic data from Google Analytics as well as a bunch of other sources, including Squarespace, Twitter, and Feedburner.
The official Twitter app (formerly known as Tweetie) is still the best Twitter client on iPhone (although Osfoora is catching up). Twitter itself is an amazing instant-intelligence engine. Two other great social media apps for iPhone are Google+ and Foursquare.
Twitter has largely replaced RSS for me for finding and filtering the latest news. However, I still track some RSS feeds and the best tool I've found to do it with is Reeder. It syncs with Google Reader so it's easy to flip between the mobile app and the desktop, plus the app lets you share to Twitter (and Facebook) and save to Instapaper and ReadItLater.
I've never fully warmed up to the Amazon Kindle e-reader, but I'm a big fan of the Kindle iPhone app. Since it was released I've read a lot more books simply because my phone is always with me and I can pull it out and read a few pages anytime I've got a couple minutes free. Alternatives: Nook, iBooks, and Kobo.
As much as I like the Kindle ebooks, I actually consume more books as audiobooks via Audible. In the past you could download these and sync them via iTunes. But Audible now has its own app, which lets you connect to your Audible library and download over the air, and even gives you a self-contained player optimized for audiobooks.
Jason Hiner is Editor in Chief of TechRepublic and Long Form Editor of ZDNet. He writes about the people, products, and ideas changing how we live and work in the 21st century. He's co-author of the book, Follow the Geeks.