Nokia OVI Suite manages and synchronises multimedia files, map-data, etc. between your phone and computer. It also interfaces with Nokia's music shop. There should have been a copy on the CD that came with your phone. In the link above select your phone & PC OS and off you go. The software is free to use but some services (data transfer, purchasing music, applications, maps, etc.) may incur charges.
It's unclear to me at the moment wheteher this software is to be used as well as or instead of Nokia's PC Suite or whether that depends on the phone OS or model.
For Mac, Nokia provides some software like which interfaces (rather crudely IMHO) with iTunes, iPhoto, iMovie, etc, but at least Nokia seem to be moving in the right direction, now that Apple's revenues exceed Micro$oft's