The process list of Activity Monitor is very nice, but oftentimes I want a lightweight alternative that is easy to start, and has very little impact on system resources. In order to achive this goal, I started with the top command as my basis. In its standard mode, top is still a bit resource hungry, so I added a few options (remove costly traversals of kernel datastructures, update every 10 seconds, sort by resident memory size):
/usr/bin/top -R -F -s 10 -o rsize
For making this command easily usable (either by double-click or by Spotlight opening), I used the Execute this command feature (Execute command in a shell activated) with the exec command at the beginning of the above command line in the Save dialog of Terminal. Together with setting the Close the window option in Window Settings... > Shell, this ensures that very little memory is consumed (the shell is replaced by using exec). The resulting Terminal window containing top can be easiy terminated by just typing q when it is active. Additionally, the scrollback buffer should be disabled in Window Settings... > Buffer.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20060816123853639