As a real estate agent and a full time road warrior, I always look forward to the next iPhone application that will streamline my workload and save time while showing houses. If you have an iPhone or are thinking about picking one up, here are ten of the most useful iPhone apps I use on a regular basis:

1. Zillow Real Estate – Zillow has received numerous accolades for their first iPhone app that allowed users to pull up homes for sale and recent sales based on their current location. Use the Zillow app (free) to show your buyers what homes recently sold for in the area and what nearby homes may also be for sale.

2. Google Maps/Earth – The Google Maps app just got 100x better with the newly introduced iPhone 3G S because it can now pinpoint your location and give you directions based on the direction you are facing. You can also look up a neighborhood and use Google’s StreetView to show clients what they can expect before driving to the home. Google Earth allows you to see surrounding terrain in vivid detail like the mountain of a nearby ski resort.

3. Loan Calculator – What If? – Have you ever had a buyer pose the question “How much would this home cost per month?” Using the Loan Calculator – What If? calculator you can easily calculate monthly payment based on their interest rate. The calculator also gives you the option to email the payment terms and information to your client from within the application.

4. Compass – The Compass app is only available with the iPhone 3G S but is certainly worth the price of admission for upgraders and new users. Using the Compass application you will become a master of feng shui by knowing which direction a home faces and where the sun will rise and set on the house your buyers are considering.

5. Trip Cubby – Up until earlier this year I always kept a pretty poor set of mileage records. Each year I would put in an earnest effort but I wouldn’t have time to add/subtract miles and write them down in the book somewhere in my glove box. Trip Cubby saves you all that hassle by putting your mileage for a trip into your phone with just a few clicks. It even saves the purpose of your trips so the next time you’re out on a tour with the Smith family you can just tap their name from the drop down and be on your way.

6. Tweetie – For today’s modern real estate agent, Tweetie will keep you connected to your sphere by giving you all the power of Twitter in a lightweight, easy to use iPhone app. Check your @replies, send out a tweet and read direct messages on the fly.

7. Urbanspoon – Are you planning to meet a VIP client who loves Japanese food and want to make a great impression? Use Urbanspoon to sort through local restaurants based on location, food type and cost. Then shake and see what Urbanspoon picks out for you! Click on the restaurant name to see local reviews and shake again to pick another place.

8. Air Sharing Pro – Designed for the true road warrior, Air Sharing Pro lets you print documents, view high resolution photos and PDFs and share files with other Air Sharing iPhone users. I always keep a folder of high-res listing images on my iPhone so I can show them to buyers who might be interested in one of my homes.

9. Flashlight – Light is quite simply a white background that turns your 3.5-inch iPhone screen into a very bright flashlight. You won’t get a lot of distance with the light but it’s perfect for illuminating dark doorways.

10. Restaurant Nutrition – Being on the road all the time, Restaurants is my favorite nutrition guide application. Load the app up and you’ll have access to a variety of fast food restaurant nutrition charts including Subway, Taco Bell and McDonalds. Now you can eat smart no matter where you are!

Have you used any of the apps above or do you know of any great alternatives? Let me know in the comments below!