Commands for CPU/Memory/Process information on Linux/Unix servers

top displays all sorts of CPU/Memory/Process information
free -m will show you stats about RAM usage in MB
uptime will show you the load average for the past 1min, 5mins and 15mins

cat /proc/cpuinfo [OR] cat /proc/cpuinfo | more will give you general information about the CPU(s) and memory on server
vmstat will give you virtual memory statistics and vmstat n will give you a run down of memory use, disk operations and cpu usage every n seconds
i.e. vmstat 1 will get a run down of memory use, disk operations and cpu usage every 1 sec