First, try downloading and installing
PocketMac. It's free, and if it works for you it will probably work well. It always has for me, but then I do have an older Mac (PowerMac G4 Dual Processor, from 2002).
Next would be to pay for
Mark/Space's Missing Sync. Folks that have had no luck with PocketMac have gotten great results with this one. Unfortunately it appears there is no free trial, which would be nice considering it's $40 and doesn't seem to work for everyone.
Last step would be to use Boot Camp or VMware on your Mac, run Windows through that, and use the regular Blackberry Desktop Software.