FTP is a pure TCP-connect protocol, and thus AFAIK "as fast as it gets" when considering TCP file transfer options.
However, there are some other products that do not run over TCP - examples are the commercial products BI.DAN-GUN, fasp and FileCatalyst. The latter product points out problems with pure TCP, and one can read more on Wikipedia, e.g. starting from Network Congestion.
What other alternatives are there? .. in particular Open Source ones? Also, one would think that this should be an RFC of sorts - a standard largish-file-transfer-specific protocol, probably running over UDP. Anyone know of such a protocol, or an initiative? (The Google SPDY is interesting, but doesn't directly address fast large-file-transfer)
There is a number of open source projects trying to tackle file transfer via UDP. Take a look at UFTP, Tsunami or UDT, each project is at a different stage of development.
Depending on the bandwidth the latency and the pocket loss you are working with, each project will produce a different result. There is a blog article that tries to compare the 3 projects, here is the link http://www.filecatalyst.com/open-source-fast-file-transfers