Not knowing your work style or requirements, I’m going to let those better than I make suggestions regarding apps that could be of use. If you are looking for suggestions try the sources below:
Apple's iPad in Business Web Page
There are dozens of apps on this page that are some of the most common apps for the iPad. Short descriptions and a quick screen shot are all you get, but there are links to the apps themselves if one of them sparks your interest.
Apple's iPad in Business Video Podcast
This is a great resource straight from the horse’s mouth. Short videos highlight specific apps that are used by various businesses. Not all the apps will apply to you, and many of them have a cost, but they are quick and well done. They highlight some functions you may not have thought of.
@Work: Apps for Business
Right within iTunes, there’s a spot where work-friendly apps are corralled. These apps may change from week to week, so stop by every now and then to see what’s new. This area includes both free and paid apps, so you can stay within a budget if necessary.
For an offline source, a book, iPad at Work, was recently published that addresses many of the functions that an iPad can be used for such as calendars, writing, presentations, and task management. It talks about these types of functions and apps that address those functions, including how-tos and screenshots. It’s available from many places in both physical and digital forms - and of course, you can read it on your iPad.
There are also many independent places where you can learn about apps and get reviews. Try Googling “iPad business reviews” and see which ones interest you.
Apps for the iPad are being developed and released everyday. If you want to be able to do something with your iPad, chances are “there’s an app for that.”
-- Julie Kuehl