Just recently purchased a new Blackberry 8830 from Sprint, it wasn’t a pleasant experience, but I really enjoy the phone. Besides the applications and themes that came with the phone there are a number of nice addons that I have found to be helpful. Links to them are below.

Google Talk for Blackberry
http://www.blackberry.com/GoogleTalk

Google Maps
http://www.google.com/gmm

IPhone Theme
http://www.eveek.com/Themes_88/iPhone-Zen-88-OTA/com_plazmic_theme_iPhone_Zen_88.jad

Black/White Theme
http://www.eveek.com/Themes_88/Bubble-Black-88-Zen-OTA/com_plazmic_theme_Bubble_Black_Zen.jad

The above applications are free, but I also purchased Texas Holdem 2 from Magmic software. It is a great way to relax/pass sometime when you are stuck at the airport or in a taxi cab.

I will add software as a find it, but also feel free to post some links if you find good stuff to share.