How can I manually replace the addressBook files on my iPhone? I upgraded from iOS 4 to iOS 5 and after it installed, I realized my contacts and apps were no longer there. I'm not too concerned about retrieving my apps, but I would really like to retrieve my contact list.

I looked at the files from my last sync and used the iPhone Backup Extractor tool to get all of the files from my sync. There I found my 'AddressBook.sqlitedb' and 'AddressBookImages.sqlitedb' files. I jail broke the iPhone and installed iFile so I can get at the files on the iPhone. When I try to edit the current 'AddressBook.sqlitedb' file with the contents of the old one, it doesn't seem to affect the contact list.

How can I retrieve my old Contact List?
The best way is to syncronize with your computer's address book.

Did you not do a backup before upgrading?  Either way, when you tell your phone to sync your address book, it will get the contacts out of your outlook or Apple address book.