The new (and IMPROVED!) Global Precipitation Climatology Project (GPCP) monthly product (Version 2.1) has arrived at the GES DISC and now is available in the TRMM Online Visualization and Analysis System (TOVAS).
For details, please check:
The new dataset is described here:
GPCP Version 2.1 Combination
"TRMM" stands for the Tropical Rainfall Measuring Mission.
For more information on Global Precipitation Analysis:
Global Precipitation Analysis, Laboratory for Atmospheres, NASA Goddard Space Flight Center