Tips4Linux.com

By using top or htop you can find out what processes are using your resources and in what ammount. Another way to do this is by launching the following command:

ps -eo pcpu,pid,user,args | sort -r -k1 | more

This will output something like

6.5  6077 user  pidgin
6.5  5535 root     /usr/X11R6/bin/X :0 -br -audit 0 -auth /var/lib/gdm/:0.Xauth -nolisten tcp vt7
6.1  7027 user  transmission
5.7  6563 user  /usr/lib/firefox-3.0.5/firefox
1.2     9 root     [events/0]
0.7  6070 user  nautilus --no-desktop --browser
0.4 29888 user  gedit
0.2  6555 user  /usr/lib/thunderbird/thunderbird-bin

…nicely formatted and structured.