What The Computer Does While You're Not There
These days there are a large number of programs that are designed to run in the background similar to UNIX daemons, with generally with far more interesting purposes. Going through my home system (a little Linux box) I picked out the most interesting ones that I have running and have documented them below.
974 pts/5 S 0:05 ./AGSatellite
Audiogalaxy, the client software for the website http://www.audiogalaxy.com is pretty much always running. This software allows me to search for music on their website, from any computer with web access, select what I want to download, and this client program (the Linux version is not full of spyware like the Windows one is) connects to whomever has the song and downloads it.
3167 pts/3 S 0:00 ./donkey
This program is the UNIX client for the file sharing services from eDonkey 2000, a peer 2 peer network (where people get whatever they want) with a website located at http://www.edonkey2000.com. The network that eDonkey uses breaks the file into parts or chunks, allowing multiple sections of the file to be downloaded from multiple hosts, at multiple speeds. The one disadvantage of this is there is the chance you will end up with large files on your system composed of mostly NULLs but has a chunk of data from the end of the file downloaded.
13471 pts/2 S 0:00 kza
Kazaa is yet another file sharing program,and I've found that it's good for several things. Relatively fast, downloads in chunks like eDonkey2000 does (this is actually the next version of the network that edonkey uses)
3181 ? RN 1309:00 /home/alan/setiathome/setiathome -nice 19 -email
The SETI@Home project takes data from radio telescopes around the world and gives them out to the internet to analyze. The client downloads data, analyses it for spikes and anomalies, and then sends the results back to the server. The homepage for this project is http://setiathome.ssl.berkeley.edu and clients for many different operating systems are available. It's great to be able to search for little green men from home.
987 pts/6 RN 1902:54 ./ghclient.x
The Genome@Home project is similar in concept to SETI@Home, but instead of looking outward into the vastness of space, this one looks inward to the human genome. Again, chunks of data are sent out to client systems, which analyze them and return the results.