Observational Data is recorded on 35 Gigabyte tapes at the Arecibo Observatory in Puerto Rico, each holding 15.5 hours of observations, which are then mailed to Berkeley. Once there, it is divided in both time and frequency domains work units of 107 seconds of data (SETI@home 2001), or approximately 0.35 MB, which overlap in time but not in frequency. These work units then get sent from the SETI@home server over the internet to people around the world to analyze.
The analysis software can search for signals with about one-tenth the strength of those sought in previous surveys, because it makes use of a computationally intensive algorithm called coherent integration that no one else has had the computing power to implement.
The program is looking for four types of singnals:
Spikes in power spectra
Gaussian rises and falls in transmission power, possibly representing the telescope beam's main lobe passing over a radio source
Triplets — three power spikes in a row,
Pulsing signals that possibly represent a narrowband digital-style transmission.
So program does alot of signal processing mostly FFT algorithms in order to find interesting signals from space that could be transmitted by extraterestrials.
Here is the info on one of the candidate signals found by Seti@home in 2004:
Radio source SHGb02+14a
now with the BOINC info available in the forum 
