Those of you who know me, know that I have been through more iPhone Apps than the average person. I have used and reviewed many iPhone Apps on my website TheAppPodcast.com. The biggest issue with buying apps is knowing if they are worth the cost or not. As a website designer I use the apps listed below. I will go into short detail as to how I use them and how they benefit me as a website designer.
Things: Things is a powerful ToDo app for the iPhone and Mac OSX platform. With both a desktop app and an iPhone app it makes it easy for me to keep my project lists up to date and synced between my iPhone and laptop. With Things I always know where I am with a project, which is important to know when I get a call or need to access that information on the road.
More info about Things for iPhone in the App Store: 
Visit the Things website: http://culturedcode.com/things/
FTPOnTheGo: At first I was skeptical of this app because of the cheesy name but this app works great. I noticed a typo on a site I was working on when I was viewing it on my iPhone. I was able to FTP into the site, edit an html page in the editor and save the changes while connected to 3G. I was in the car waiting for my wife to get off of work. How cool is that?
It is often that my clients call me with mini fires that need putting out. This app allows me to make some quick changes on the fly. Before this I had to SSH into my website and edit pages that way. FTPOnTheGo makes this much easier.
More info about FTPOnTheGo in the App Store:
Analytics: This goes with out explaining. With the Analytics app for the iPhone you can view all aspects of your website analytics from Google Analytics. I have setup custom dashboards that display the information I want to see quickly. This also makes it easy for me to check in on my clients to see how their website is performing. Nice graphs and plenty of information. I have accessed this information when giving presentations and to show to my clients when spikes in traffic happen.
More info about Analytics App in the App Store:
BlogPress: BlogPress allows you to create content on a variety of different platforms from one app. It works great with WordPress blogs and I use it to update my blog from the road. You can upload photos right into your blog post from your camera roll or take a photo and BlogPress will load it right in. If you have a Picasa album you can import images from there as well.
You can manage multiple website with this app. BlogPress supports Blogger, MSN Livespaces, WordPress, Movable Type, TypePad, Live Journal, Drupal, and Joomla.
More info about BlogPress in the App Store:
Instapaper: I am always coming across great articles and other websites I want to look at later. Instapaper lets you create a list of those sites and categorize them. Instapaper is integrated with several Twitter apps such as Tweetie and Twitterrific. I have also added a bookmarklet to my browser on my laptop and iPhone to quickly add websites to Instapaper when I want to save them to read at a later time.
More info about Instapaper in the App Store:
Ego: Ego allows you to view basic information about your online existence. You can load in your Twitter account, Google Analytics, Google Page Rank, Feedburner Stats, Mint Analytics, and Squarespace account info. Ego presents this info to you in an easy to read format. What is great about Ego is that it gives you quick access to basic information about your online life. I use it to keep an eye on my websites and the websites of clients that have monthly SEO management accounts with jeradhill.
More info on Ego in the App Store:
TouchTerm: If you really need to, you can access your server and execute shell commands. I have ran tar backups on sites before, changed file directories, fixed permissions and renamed files using this app. Now that I have FTPOnTheGo I rarely use TouchTerm but in the instance I need to run a command, it is more capable then the FTP App.
More info about TouchTerm in the App Store:
google analytics also provide great data about website statisitics:~’