One of my favourite applications on my dear old iPAQ is Pocket Informant. The iPAQ is now mainly a (rather large) music player.
I was delighted to find that PI is now available for my Blackberry
Excellent news - really looks good and has many great functions - everything seems very easy to see ( I love the Agenda view) and adding new stuff is easy. My categories etc. for GTD work just fine.
This version lacks things that I would like from the Windows version: hierarchies of tasks, links from tasks to contacts are a couple that I used to use a lot. As this is an early version on this platform I am confident there will be new features coming along regulalrly