To get the best from all possible contributions its advisable to provide as much details as possible regarding the question and data you are working with.

You have different TRMM products and datasets can be downloaded from different sources in different formats.

Monthly data can be downloaded from http://www.geog.ucsb.edu/~bodo/TRMM/ as geotiff.

Global near real time data (3H and 7D) can be downloaded from http://pmm.nasa.gov/TRMM/realtime-3hr-7day-rainfall as non georegistered GIF.

TRMM Ancilary data can be downloaded from GES DISC http://mirador.gsfc.nasa.gov/cgi-bin/mirador/presentNavigation.pl?tree=project&project=TRMM as HDF files.

For Near Real Time data you'll have to georegister the image.

You can also get all there products as kml and linked tiles from  http://mirador.gsfc.nasa.gov/cgi-bin/mirador/presentNavigation.pl?tree=project&project=TRMM

http://www.geog.ucsb.edu/~bodo/TRMM/

http://pmm.nasa.gov/TRMM/realtime-3hr-7day-rainfall

http://mirador.gsfc.nasa.gov/cgi-bin/mirador/presentNavigation.pl?tree=project&project=TRMM

Thanks for your detailed answer hoping to be positive for my research.