Recently I found three new apps for my phone and I love adding them to my walking time. I have a Droid and love it. As I start doing more and more miles alone it's nice to have the distractions.
One is Endomondo. It tracks distance and time walking - which a lot of apps do - but what I like is it tells me when I've gone a mile and gives me my times. Every mile after that it gives me my splits. The uploads to a web site. The web site has lots of fun stuff - like how many times I've walked to the moon (none) and how many times I've walked around the world (.003 still a ways to go).
Another app I'm loving is my new podcast player called BeyondPod. I can stream or download podcasts. I like having them pre-downloaded then it doesn't seem to take as much of my battery life. I'm catching up on all kinds of stuff.
The third app is a mobile version of GrooveShark, my favorite online music player, called TinyShark. I have had so many problems with Pandora on my phone that I took it off and switched to this one. Same concept except you can actually play the song you like.
One other addition to my phone isn't really an app but Dennis has been downloading audio books for me and I love listening to them from my phone.
Walking alone isn't boring any more!