Newish vagrant (1.4+) has built in NFS share support. You can share filesystems between the host and the VM using NFS. If you’re like me, and running on VMware Fusion, this is a huge win, because you get to dodge the terrible performance and massive bugginess of vmhgfs. In particular, this issue where files are truncated was driving me spare.
The documentation for the feature is here. Go forth and use it, but one word of warning – on a mac it starts a bunch of RPC services (NFSd, mountd, …) which listen on all interfaces, not just the bridge with the VMs. So you might want to firewall those off.