I think my iPhone is the coolest invention ever (well that and my Nook). I always try and get free apps or 99 cent apps (call me cheap). Here are some reviews of my favorite apps that keep me organized:
My first favorite app, isn't really even an app, it is the calendar on my iPhone. I put everything here, and sync it with Outlook. I still keep a calendar on the fridge, but my phone is with me everywhere, so I always feel like I know what is going on!
I also like Stick It, 2Do and ShopShop.
Stick It simply creates sticky notes for you. I use this all the time when I'm making "To Do" lists."
2Do really is great for projects. I use it quite a bit for my job, but I've also used it when planning parties or events. It is a more expensive app, but I have 2Do Lite, and love it.
ShopShop is an easy, quick grocery list maker.
For traveling, I like MapQuest and AroundMe.
MapQuest is like a built-in GPS! It has been great, especially traveling in unfamiliar big cities.
AroundMe identifies your position and allows you to choose the nearest Bank, Bar, Gas Station, Hospital, Hotel, Movie Theatre, Restaurant, Supermarket, Theatre and Taxi.
Probably the app that has saved me the most time and money is RunKeeper. I used to run a new route, then have to drive it to figure my distance. This app calculates your time, distance and gives you your current pace. I use it when biking, walking and running. It was free and worth every penny!
Since I'm a big fan of Mint.com to help with budgeting, the Mint.com app is another favorite of mine!