Computer Tips - What commands can I use to see how much memory is used?

Date: 2009may3 OS: Linux Level: beginner Q. What commands can I use to see how much memory is used? A.
free - Display amount of free and used memory in the system slabtop - Display kernel slab cache information in real time vmstat - Report virtual memory statistics top - Show busy processes htop - top with color atop - Advanced System & Process Monitor ps - Show processes