To obtain a ps(1)-like list of Windows processes, use pslist from pstools. [tlist?]Alternatively, use get_process_ids [1] from the TWAPI package.
To obtain a ps(1)-like list of Solaris or Linux processes, use procfs.tcl from http://inferno.slug.org/tarballs/procfs.tcllavaps
In Alpha, processes is a command that returns (drumroll) a list of descriptions of running processes (well, rather applications). Excerpt from join [processes] \n:
loginwindow lgnw APPL 5793 0000000000020001 /System/Library/CoreServices/loginwindow.app/Contents/MacOS/loginwindow
Dock dock APPL 8123 0000000000060001 /System/Library/CoreServices/Dock.app/Contents/MacOS/Dock
SystemUIServer syui APPL 8189 0000000000080001 /System/Library/CoreServices/SystemUIServer.app/Contents/MacOS/SystemUIServer
Finder MACS FNDR 8190 00000000000a0001 /System/Library/CoreServices/Finder.app/Contents/MacOS/Finder
iTunesHelper ithp APPL 9456 00000000000c0001 /Applications/iTunes.app/Contents/Resources/iTunesHelper.app/Contents/MacOS/iTunesHelper
iCalAlarmScheduler ???? APPL 9466 00000000000e0001 /Applications/iCal.app/Contents/Resources/iCalAlarmScheduler.app/Contents/MacOS/iCalAlarmScheduler
{Acrobat Reader 5.0} CARO APPL 102108211 0000000006e40001 {/Applications/Acrobat Reader 5.0/Contents/MacOS/Acrobat Reader 5.0}