Nvidia have released CUDA driver 6.0.51 which is required for CUDA support on Mac OS X 10.9 Mavericks. Note: Quadro FX for Mac or GeForce for Mac must be installed prior to CUDA 6.0.51 installation

An alternative method to download the latest CUDA driver is within Mac OS environment.  Access the latest driver through System Preferences > Other > CUDA.  Click 'Install CUDA Update'.

There are a number of GPU-accelerated science applications described on the GPU Science Page.