Rainfall projects:

Measuring rainfall over ocean areas is something that can only
be done via satellite. Would suggest looking at the
Tropical Rainfall Measuring Mission (TRMM) which is a joint
mission between NASA and the National Space Development Agency
(NASDA) of Japan designed to monitor and study tropical
rainfall; information and data are available at
http://trmm.gsfc.nasa.gov/

The Global Precipitation
Climatology Project(GPCP) which is an element of the Global
Energy and Water Cycle Experiment
(GEWEX) of the World Climate Research program (WCRP). It was
established by the WCRP in 1986 with the initial goal of
providing monthly mean precipitation data on a 2.5 x 2.5 degree
latitude -longitude grid for the period 1986-1995. This was
recently extended to the year 2000; the link to GPCP is on the
web at http://cics.umd.edu/~yin/GPCP/main.html