Inter-Tel purchased conferencing and collaboration company Linktivity a while back and has now integrated much of the functionally in the Linktivity products into version 3.0 of their Unified Communicator product. With this release, you can have an ad-hoc web meeting and collaboration. You can share your desktop, take advantage of whiteboarding and stream video back and forth as well. Oh yes, you can send files as well. Inter-Tel has always been a technology leader and this product is a natural extension of the PBX and in my opinion will be common on all PBXs in the near future.
You have no-doubt read about Just in Time Communications, the term I use to describe the technologies that wring efficiency out of communications. The above product embodies these efficiencies.