Although the pickings are slim right now, my favorites are:

1. Inrix

2. CommuteWX

3. Pandora

4. CarMedia Player

5. Beej!

6. DashCommander

I use Inrix and Beej! every single day and they are great. I like the weather CommuteWX provides and the app has gotten progressively better from the first version. Aside from the scrolling issues, CarMediaPlayer is much better than iPod. I'd like to see a bit tighter integration with DashCommander but for what it is, it's great.

What are some of yours?

Being an Android user with ARLiberator, I can use any app on the phone without being restricted to what Pioneer want you to have access to.

Don't use any of the Pioneer apps as they are on the whole pretty poor compared to what else is out there.

I am using AppRadioEx so I can use any app on the phone as well. I am referring though to apps specifically made to run on the head unit - not Pioneer-based apps.

Waze

Carmediaplayer

Dash Command

Extra Mile

I really hope Pioneer can get Spotify on board. That would more or less make things perfect. Pioneer's pandora overlay is nice but I never use pandora anymore. 

what is beej exactly because no video description available ?

for me best apps
IGO navigation
Waze gps
Streamhifi
EC touch
Carmediaplayer

If google map could be officialy available...

Beej is a directory/nav app. Pretty sweet.