The best way is to import them into Outlook on your pc, then sync Outlook to your BB through BlackBerry Desktop Manager.
Additionally, Google Contacts allow users to import contacts from various file formats stored on their pc. You could use Google to import your contacts and set up wireless sync to your BlackBerry. I have found that Google often has issues with contact formatting when syncing to a BlackBerry so it's not my first choice. Little things like making a personal phone number a work phone number, etc. This can cause duplicate contacts and be a pain it the arse to sort out. On the plus side, Google contacts will be a real-time backup solution once you have it set up. And you just cannot have too many backups.