A pre-release of GPULib was made available today. GPULib is a library of common scientific computational routines that use modern graphics processing units (GPUs) to improve performance. I saw speedups of 5-50 times faster than normal IDL code for example code I was writing. Vectorized code that is still not fast enough can be improved with GPULib.
Bindings for Java, Python, MATLAB, and IDL are available. The IDL bindings are fairly simple to use and have a compatibility mode that allows running the code even without a GPU (performance was approximately equivalent to normal IDL code for the examples I wrote).
The documentation lists all the routines available (IDLdoc 3.0b3 spotted in the wild!).
Full disclosure: I work for Tech-X Corporation and worked on the IDL bindings and examples for GPULib.