Cache-Oblivious Implicit van Emde Boas Binary Search Trees, released today under the University of Illinois/NCSA Open Source License.
This is a very short bit of C++ code that demonstrates how to derive and implement cache-oblivious implicit van Emde Boas BSTs.
It has not been tested very much, but both algorithms for iVEB BST search and construction have been proven correct (although not independently verified by anybody but me). It was written to facilitate writing a proof or two, rather than for actual use as a cache-oblivious data structure.
As such, it was written without performance or elegance in mind, but rather with the goals of comprehensibility and readability.