Get a python program I've written onto Blackberry or other mobile platform?
Given the number of platforms you listed, 

iPhone, Symbian, Android, BlackBerry,
  and Windows Mobile

I'd suggest you look into a web framework you can integrate your logic into.  I know Django is quite popular.  Putting a web-frontend on your app does mean your users do have to be connected to the Internet to use your application and you have to have it hosted publicly on the Internet- but I think the Pros far outweigh the Cons.
If you develop your application to run on the phone, you have to address every platform you want it to run on; conversely, if you host your app on the web, any standards compliant browser should be able to present your application to the user.  This also means the application isn't tied to the device. Should the user change phones, or loose their phone- the application (and their data) is not lost or compromised.  
This also means the users can access the application from their desktop, tablet, nettop, PS3, wifi-connected toaster etc.
I know this isn't really what you are looking for; its a suggestion to the fundamental design of your application; but with the little info you've posted about the application- there was nothing suggesting it 'can not' be hosted on a the web using standards compliant technologies.
FWIW- making a mobile application more 'future proof' will only pay out in the end. mobile platforms change faster then just about any other consumer technology.
My $0.02
The said program runs only on my PC as of now. 
I've been searching through StackOverflow, and I've found out about RhoMobile's Rhodes which allows you to write the app in Ruby once and run it in multiple mobile platforms: iPhone, Symbian, Android, BlackBerry, and Windows Mobile. Is there anything similar for Python? If not how would I go about doing it?
Thanks in advance!