Over 8 million iPads have been sold and yet one of the most common questions I’m asked when someone sees the one that I carry with me (everywhere) is “has that been useful for you?” The answer is an absolute yes – more useful then I ever would have thought. The hardware is beautiful and packs some amazing tech, but as always the most important thing is the software that’s installed – and for an iPad that means apps.

There are now more than 300,000 apps available for the iPhone and iPad, but don’t worry. I’ve cut through the clutter to give you a list of the must-have apps that will make you more efficient while in the office, in the sales office, or on the job site.

Todo
First things first – you need to get (or stay) organized. Todo helps you focus on what matters most, keep track of everything, and allows you to integrate the Getting Things Done (GTD) methodology or your own. It’s good for short notes as well (use Soundnote for long in-depth notes at meetings). It also syncs to the cloud so you can view your lists/notes from any web browser. Very intuitive.

Teamviewer
With TeamViewer you can remotely control any computer as if you were sitting right in front of it – even through firewalls. All you have to do is start a small application, which does not even require installation or administrative rights. It allows me to have access to the speed and power of my laptop at the touch of my fingertips (as well as access to my company’s files on the internal network). This app may not be your IT manager’s favorite thing, but it will quickly become one of yours.

PDF Highlighter (no longer a top pick – see updates below)
Highlighter is a powerful PDF annotation tool. You could also use it to read your PDF files, but iBooks does that better. You can add text notes do freehand sketches of a custom option or change order — all saved directly to the PDF file, so that you can review them later on your Mac or PC using standard software like Acrobat Reader.

Adobe Ideas
Adobe ideas is basically like an “Adobe Illustrator Lite.” You can draw on a canvas to make notes or communicate ideas. The best part is that you can use any photo on your iPad as the canvas to allow you to draw over the picture. Want to review how the new landscape plan will make that old spec home feel new again? Or perhaps you just want to show the trim carpenter exactly how you want that mantle around the fireplace to look – this app does the job!

Dropbox
Dropbox allows you to sync files from multiple sources (home pc, work pc, iPad) and is one of the best ways to organize files for your iPad. Many other apps support Dropbox as well, so for example if you need to open a blueprint file in PDF Highlighter to mark a custom change… you can open it right from Dropbox.

SoundNote (no longer a top pick – see updates below)
Have you ever wished you had more detailed notes of important meetings you attend? Would you like to have 100% complete notes, and only need to type a handful of words? SoundNote is the answer! It records audio of the meeting, and syncs the timing of the audio with the words you type on your iPad. The final result? All you need to do is type the headings when the topic changes and you’ll pick up playback just as you start talking about that subject.

Skype
The same powerful voice communication tool is available for use on your iPad (and video calls on your iPhone as shown by Mike Lyon and Zach Schabot). Grab this one now for the audio alone, and when the new iPad is released with the cameras then you’ll be able ready to join the video calling party.

Flipboard
You don’t want to fill up your iPad with too many redundant news readers to stay on top of current events and social trends… so just grab the best news aggregator around and make your own digital magazine based on topics you enjoy reading about. It also keeps you informed on your Facebook and Twitter connections by displaying them in a fun tabloid layout. There’s a reason why many web sites named it the app of the year.

Golfshot
You can’t be working ALL the time, and this app will make even those who have trouble breaking 100 have a blast on the golf course. It uses the built in GPS to follow you around the course and give you accurate yardages – and it allows you to track your stats, club selections, etc for good laughs after the round is over.

Of course, you also need to grab the full array of social media apps – Facebook, Twitter, Foursquare, LinkedIn, etc… that goes without saying (although you’ll be amazed how much you can do in Flipboard).

I’d love to hear what apps you’ve discovered that you can’t live without. Let me (and everyone else) know by commenting below!

UPDATE: December 26th, 2012
Here are some new updates and additions to the list.

PDF Expert
If you find yourself working with PDF files a lot then this is by far the best one for you. It allows you to sync directly with a Dropbox or other cloud service for easy access to your files. This feature alone makes it a must-have, but it still has all the same functionality that PDF Highlighter had as well.

Notability
If you liked the Soundnote app, but wished for more organization for your files then this is the one for you. There is no app for iPhone yet from this developer, but you can export all your notes to dropbox for viewing on your phone. This app has everything AND the kitchen sink for note takers.