I have released a major update of the SdFat library http://code.google.com/p/sdfatlib/downloads/list
The Arduino SD.h library is a wrapper for an older version of SdFat.
Here is a post that compares some features of the new SdFat with the version of SD.h that was released with Arduino 1.0 beta1.http://forums.adafruit.com/viewtopic.php?f=31&t=21844
The new version of SdFat includes support for C++ style I/O streams plus many other new features. The new features are demonstrated in about 20 new examples.
Additional data logging libraries and example programs for GPS modules and fast ADCs are here http://code.google.com/p/beta-lib/downloads/list