like nacho & f2 with outlook or Google sync but id have to say Google sync is the way 2 go its awesome if i add a contact in my blackberry it automatically adds it 2 my other phones i have Google sync on, plus like you want i can add contacts threw my computer.
Google Sync is a great and free option, plus it works. Keep in mind that, not being tailor made for BB, some contact info fields do not map to Google Contacts, like PIN numbers.
