Determining 64-bitness of your CPU

It looks like /proc/cpuinfo isn't the only way to find out whether your CPU is 64bit capable. In an effort to determine the most reliable way to find out this information I came across this page. A quick summary:

If you see any output from the following command, you're running a 64-bit capable CPU.

grep ^flags /proc/cpuinfo | grep ' lm '

The following command, if it exists on your system, will tell you the width of your physical and logical CPUs:

lshw -C cpu | grep width

The lshw command is available natively on my Ubuntu 9.04 system and is available from rpmforge.org for RHEL5 and CentOS5 systems.