Is there a list of Linux processes/services and their use?

I just did a base install of Debian and have been looking at runlevels. My installation contains the following:

• acpid
• atd
• bootlogs
• console-setup
• cron
• exim4
• halt
• kbd
• keyboard-setup
• killprocs
• kmod
• motd
• networking
• nfs-common
• procps
• rc.local
• reboot
• rmnologin
• rpcbind
• rsyslog
• sendsigs
• single
• sudo
• udev
• udev-mtab
• umountfs
• umountroot
• urandom
• x11-common

I know what a few of those are, and can guess a few more. The remaining I can look inside /etc/init.d/ and figure things out too. With that said, I would prefer some type of online list where I can do a search for each process, see exactly what it does, and determine whether or not I need it.

For example, there's the Services Guide for Windows XP that shows the list of services for Windows XP, gives a brief description, and recommendations as to whether or not you actually need it.

Does something like that exist for Linux? It doesn't have to be for a specific distro.

Thanks for any help! :)